What is an LLM (large language model)?
An LLM, or large language model, is an AI model trained on huge amounts of text so it can read, write, summarise and reason in natural language. It is the engine behind assistants such as ChatGPT, Claude and Gemini.
You do not need to know the maths to use one well. What matters is understanding what LLMs do brilliantly, where they fail, and how to give them the right instructions and information.
What an LLM means (and why it matters)
LLMs turned language into something software can work with. That means emails drafted in seconds, long documents summarised, customer questions answered, and data pulled out of messy text. Almost every modern AI tool for business is built on one.
How an LLM works
| Idea | Plain English |
|---|---|
| Training | The model learns patterns from a vast amount of text |
| Tokens | Text is split into small pieces the model reads and writes |
| Prediction | It writes by predicting the next token, again and again |
| Context window | How much text it can consider at once |
| Prompt | Your instructions and information, which shape the answer |
| Temperature | How varied or predictable the answers are |
What LLMs are good and bad at
| Good at | Weak at |
|---|---|
| Drafting and rewriting text | Facts they were not given (hallucination) |
| Summarising long documents | Exact arithmetic on large numbers without tools |
| Extracting data from messy text | Knowing recent events, unless connected to search |
| Answering from documents you provide | Following vague instructions |
How to use an LLM well, step by step
1. Give a clear task and role
"You are a support agent. Reply to this customer in under 100 words."
2. Provide the information
Paste the policy, the data or the document. Do not rely on what the model might know.
3. Specify the format
Bullets, a table, an email, a fixed length.
4. Check the output
Verify numbers, names and claims before you use them.
A worked example
A property manager pastes a 30-page lease into an assistant and asks for a one-page summary of rent, deposit, notice period and repair duties, with page references. It takes a minute instead of an hour, and the page references make checking easy.
Common mistakes
- Trusting facts without checking. LLMs can invent details.
- Vague prompts. Clear instructions give much better results.
- Pasting sensitive data into personal accounts. Use business plans with data controls.
FAQ
Which LLM is best?
It depends on the task. Compare the main assistants in ChatGPT vs Claude vs Gemini and test them on your own work.
How much do LLMs cost?
Personal assistant plans are about $20 a month. Through APIs, you pay per token, often a fraction of a cent for a typical request.
Can an LLM learn about my business?
Yes, mostly by giving it your documents at question time (RAG) rather than retraining it.
Final verdict
LLMs are the most useful general-purpose tool most businesses have gained in years. Give them clear instructions and real information, check their work, and they save hours every week.
Want LLMs working inside your business?
We build custom AI systems and AI voice agents on top of leading models.