A prompt is not a conversation. It's a component contract.

Most of us use LLMs by trial and error. This post gives you a structure: the building blocks of an LLM, and a reusable template for writing production prompts.

What is an LLM?

Foundation models are very large models pretrained on internet-data; that's what builds Generative AI. With a foundation model, you can adapt one pretrained model to many tasks.

A Large Language Model (LLM) is a foundation model for text, and at its core, the same FM can be used for many tasks: summarisation, classification, translation, code generation.

So what an LLM does is predict the next word (next token) in a sequence. At each step it checks the surrounding context of what it has seen so far and then produces a probability distribution over the possible next tokens. Running this in a loop produces fluent, coherent new content. So basically, an LLM gets text and returns text. The input is called the prompt and the output is called completion.