The wire format is fairly straightforward if you've seen a few binary encodings. The language used to write the schemas isn't quite as simple and regular as you might hope, though.

> Maybe you mean something besides the wire format. In that case, good luck, because that shit ain't protobuf.

Naming's hard :) Being really pedantic, I think even Google calls the schema description language "Protocol Buffers" and uses phrases like "the Protobuf binary format" or "the Protocol Buffer wire format" to refer to the wire format. Colloquially, it's never confused me to just use "Protobuf" for both.