Mary Fung
noteJune 18, 2026

What is an LLM?

A plain-English guide to what large language models are, what they are good at, and where leaders should be careful.

An LLM is not a brain, a database, or a magic intern.

It is a system trained to generate useful language based on patterns. That sounds small until you remember how much business work is made of language: emails, reports, meeting notes, policies, research, customer messages, code, tickets, proposals, and strategy documents.

LLM stands for large language model. "Large" means it was trained on a huge amount of material. "Language model" means it learns patterns in language and uses those patterns to predict what should come next.

That is why it can write a summary, explain a concept, draft an email, translate technical language, brainstorm options, and answer questions in a way that feels surprisingly human.

But the important word is feels.

An LLM can produce a confident answer without actually knowing whether the answer is true. It does not have judgment. It does not understand your business unless you give it the right context. It does not automatically know your risk tolerance, customer promises, legal constraints, data definitions, operating model, or internal politics.

That is why leaders should not think of an LLM as an expert.

Think of it as a very fast language engine that can help with thinking work when the task is clear, the context is useful, and a human still owns the judgment.

What LLMs are good at

LLMs are useful when the work involves language, structure, comparison, summarization, or transformation.

They can turn rough notes into a cleaner memo. They can compare options. They can explain technical material in plain English. They can generate first drafts. They can find patterns in feedback. They can help a team move from a vague idea to a clearer plan.

They are especially useful when the answer does not need to be perfect on the first try and a human can review the output.

That is the important operating model: AI is often best as a drafting, translation, and reasoning partner. It is not automatically a final decision-maker.

What LLMs are bad at

LLMs struggle when the task requires guaranteed accuracy, current facts, private business context, precise calculations, or accountability.

They may invent facts. They may cite sources that do not support the claim. They may miss edge cases. They may produce a polished answer that hides weak reasoning.

This is one of the biggest risks for executives: AI can make mediocre thinking look finished.

A messy human draft often looks messy. A weak AI draft can look board-ready. The polish can be misleading.

The executive mental model

The best question is not "Can AI do this?"

The better question is:

What would need to be true for us to trust AI with this part of the work?

That question moves the conversation from hype to operating design.

For low-risk work, the answer may be simple: a clear prompt, a quick human review, and no sensitive data.

For higher-risk work, the answer may require approved source material, access controls, audit trails, testing, human sign-off, and a way to catch errors before they reach customers or decision-makers.

The model matters. But the system around the model matters more.

Questions leaders should ask

Before approving an AI workflow, ask:

Those questions are more useful than asking whether the team is using the "best" model.

The serious AI conversation is not about whether an LLM sounds smart.

It is about whether your organization knows where the model is useful, where it is risky, and who remains accountable when the output leaves the chat window.

← back to the field