Level 1: Foundation Models

This is the layer underneath almost everything else in the AI Levels stack: the raw foundation models that power the assistants, tools, and agents you'll meet in Levels 2 through 5. You'll probably never touch this level directly, and that's fine, but understanding what it is makes every level above it make more sense. Four short lessons: what a foundation model actually is, the major models compared, where this level actually shows up for you, and why the rest of the stack builds on it.