Within a single 24-hour period in July 2023, one major newspaper ran two strikingly opposed headlines about artificial intelligence: first, that AI could cure all disease and end poverty, and the next day, that it might kill every person on Earth simultaneously. That whiplash isn’t just media hype; it reflects a deeper confusion about what these systems actually do.

Part of the problem is that defining artificial intelligence is harder than it sounds. AI researchers don’t even agree on what “intelligence” means. Some point to reasoning, others to planning or self-awareness. AI systems can mimic pieces of this, but never all of it.

For practical purposes, a useful way to think about it is this: AI is software that can perform tasks that would normally require human thinking, such as learning or making decisions. However, it does this without possessing genuine understanding, consciousness, or moral agency, a limitation that matters more than it might seem.

AI is a broad field that includes areas such as computer vision, robotics, and older rule-based systems. Among these, one category has become especially visible: large language models, or LLMs. These are the systems behind tools like ChatGPT, Gemini, Copilot, and Claude. If you have ever typed a question and gotten back a polished paragraph, you have used one. These systems are already shaping how people work, learn, and communicate.

A simple example from everyday language helps explain how they work. In a sufficiently large sample of English text, the letter E appears roughly 13% of the time, while the letter Z appears less than 0.1%. Certain letter pairs — TH, HE, IN — are far more common than others. Extend this logic to three-letter groups, then four-letter words, then whole phrases, and a clear picture emerges: written language is not random. It follows dense, measurable statistical patterns.

Large language models take this idea and scale it up dramatically. Instead of letters, they work with pieces of words and text, sometimes whole words, sometimes parts of words, which they process as units. During training, the model is shown massive amounts of text, and learns to predict the next word in a sequence by adjusting itself based on patterns in the data. Over trillions of such adjustments, the model gradually builds a highly complex picture of how words and phrases relate to one another in human writing. Because human language reflects how we think, a system that learns these patterns can often mimic reasoning, explanation, and even creativity, but without actually possessing those abilities.

Think of it as an improv artist: it generates responses on the fly, drawing on everything it has seen during training, and the results can be impressive, even surprising, but it is not consulting a script or drawing on genuine understanding. It is simply a system that has become extremely good at predicting what sounds convincing based on patterns it has seen before.

When you type a prompt into ChatGPT, the model does not look up a stored answer. Rather, it asks itself, in effect: given everything I have seen, what sequence of words would most plausibly follow this input? It then generates a response one word at a time, each word selected based on probability, though this happens so fast it feels instantaneous. The result is essentially a continuation of the text it has been given, shaped entirely by the patterns it learned during training.

The most important point to understand is this: an LLM is a predictor, not a knower. It does not store facts the way a reference book does, and it does not reason the way a scientist does. It has been trained on vast amounts of text from the internet and other sources. As a result, it has become extraordinarily skilled at producing text that resembles it. That is a genuinely remarkable capability, but it is a fundamentally different thing from knowledge or judgment.

This distinction is not just theoretical — it has real consequences. Because LLMs are designed to produce fluent, coherent text, they can generate responses that sound confident and polished but are simply wrong. This is known as a “hallucination,” and it isn’t a glitch so much as a side effect of how the system works: it is always trying to produce a likely-sounding answer, even when it lacks reliable information.

For example, ask an LLM to write a biography of someone who does not exist, and it may produce a detailed and believable life story. It does this because the result fits the pattern of typical biographies. Current models have no built-in way to check whether the information is true. It is only trying to produce something that sounds credible based on what it has seen before.

Hallucinations are only one example. There are other important limitations. LLMs have a knowledge cutoff date and cannot access real-time information unless connected to external tools. They can also contradict themselves within a single long conversation because they have no reliable memory of what was said earlier. None of this is obvious when you use them — and that is precisely the problem. The responses are fluent and confident, which can create a strong impression of competence and authority.

These limitations are closely tied to another basic principle in computing: the idea of “garbage in, garbage out.” An LLM can only work with the data it was trained on and the input you give it. If the training data contains errors or bias (and all large datasets do), those problems show up in the model’s output. And if your prompt is vague or based on a false premise, the model will often give you an answer that sounds reasonable but simply builds on that mistake instead of correcting it.

This puts more responsibility on the user, who cannot rely on the system alone to guarantee accuracy. AI-generated content should be treated with the same skepticism you would apply to an anonymous tip or an unsourced article. The model will not tell you when it is uncertain unless you ask. It will also not avoid guessing just because a question requires expertise it lacks.

Some of these risks are addressed through a process known as alignment. When LLMs are first trained, they learn from large amounts of human-written text, which includes both helpful and harmful material. Left on their own, these models can produce outputs that are unsafe or deeply objectionable. Alignment is what makes a system refuse to answer harmful questions or try to give balanced, cautious responses on sensitive topics. But alignment is not a perfect filter. It is designed and applied by human teams. It reflects their choices, assumptions, and blind spots, and can introduce limitations and biases of its own.

Even with alignment, another challenge remains — one that comes from us rather than the system. Humans are wired to treat anything that talks like a person as a person. When a system speaks to us in fluent, responsive, emotionally attuned language, our instinct is to attribute understanding, intent, and even feeling to it. This instinct has served us well throughout human history. If something could talk, it was another person. But it can mislead us when applied to a system that is simply generating text based on patterns.

An LLM that says “I understand how difficult this must be for you” is not expressing empathy. It is producing language that fits the context. The warmth is part of the pattern, not a sign of real understanding. This matters because it can create a false sense of trust. People may rely on AI as we rely on human experts in situations where mistakes carry real consequences, such as medical advice, legal questions, or financial decisions. These systems should not replace expert human judgment in those areas. A response may sound fluent and confident, but that does not mean it is reliable.

Despite these limitations, large language models are not useless. Rather, it means they need to be used with care. LLMs are powerful tools for working with text. They can help you write, revise, summarize, and translate. They can explain complex ideas, spot patterns in large amounts of information, draft emails and reports, generate code, or help you think through an idea. These are real strengths, so ignoring them would be a mistake.

What matters is understanding what you are working with. Like that improv artist, an LLM is always performing on the fly — and the performance can be impressive. But it is not an authority or a fact-checker, and it cannot replace real expertise. You still need to verify important claims and apply your own judgment.

The headlines that AI might cure disease or wipe us out reflect the same reality: this is a powerful technology that many people still misunderstand. Large language models are pattern-based systems. They predict text, but do not understand it. They can be creative and useful, but they are not reliable arbiters of truth. Used carefully, they can improve how you think and work. Used carelessly, they can just as easily reinforce your mistakes.