Hi there!
Presumably, if you're reading this, you want examples for how to use ggez.
We recommend starting with 01_super_simple.rs
to get started and going down the numbered examples from there.
The numbered examples try to start from the simplest program possible and move on to more sophisticated ones, ending in full games.
The non-numbered examples show off the details of various specific parts of the library, such as generating meshes, messing with shaders, or digging into the details of input and settings options.
For a general overview of the API, or want to know what ggez is capable of, you might want to go to https://docs.rs/ggez/ and read the module docs for each module. There's a paragraph or two for each module introducing what it contains and how the various subsystems work.