What Cursor actually is
Cursor is a fork of VS Code with models wired through the editor. You get chat that can see the file, inline edits, tab completion trained on the surrounding code, and an agent that can read, write, and run across the project.
It uses several model providers. The brand is the editor loop, not a single API. If you pulled the models out, you would still have VS Code. If you pulled the editor out, you would have ChatGPT with extra steps.
The value is the combination: the model sees the right context, proposes a diff you can review, and stays in the place you already write software.