Step 1 — A Language Model Reads Your Words
The first thing that touches your prompt is a language model. This is the part of the system people mean when they say "LLM," and it is worth understanding because it is the part you actually talk to.
What a language model is, for an artist
A language model is a program that has read a colossal amount of text and learned which words tend to go with which other words, in which contexts. That's genuinely it. From that one ability it gets a surprisingly deep working knowledge of what things mean — that cerulean is a blue, that chiaroscuro implies a hard light source and deep shadow, that a Dutch angle is a tilted camera, that Bauhaus and Art Nouveau are not the same century.
It is not looking anything up. It has no dictionary. It has a learned sense of how these words sit next to each other, and that turns out to be enough.
What it does with your prompt
It converts your sentence into a compact numerical summary of its meaning — not a list of your words, but a representation of what you were getting at. Two prompts that mean nearly the same thing land in nearly the same place; two that mean different things land far apart.
This is why "a decrepit seaside hotel" and "a run-down hotel by the sea" give you similar images, while changing one adjective from decrepit to opulent changes everything.
Two flavours you'll meet in the wild
- A plain text encoder. Older and open-weight image tools use a relatively small model that just reads your words. It is literal. It does not reason, it does not fill gaps, and it does not ask what you meant. Give it a vague prompt and you get a vague image.
- A full conversational model. Tools built on chat assistants (ChatGPT's image generation, Gemini's, Copilot's) run your request through a proper reasoning model first. It will expand "a cosy reading nook" into a paragraph of specifics before any painting starts. Convenient, but it means the model is making creative decisions on your behalf — which is why the same prompt twice can give you two quite different rooms.
Knowing which of these you're talking to is the single most useful thing you can know about a tool. It decides how you should write.