Glossary — Tools
API
An API is the interface one program uses to request a service from another — with AI, the way to put a model to work inside your own software.
1 tokensAPI
Simply put#
The chat interface is for a person. The API is for a program. Same model, no window: your application sends text and gets an answer back.
Example#
When your shop's support replies automatically, nobody is sitting in a ChatGPT window behind it — that is an API call.
Why it matters to you#
API use is billed per token rather than per month. That makes cost predictable, but it also means a badly written prompt costs money every single time it runs.