An RzBin struct contains information about the binaries in a Rizin program.
Most importantly, it contains binfiles - an RzList containing RzBinFile.
The main instance is accessible in the bin field of an RzCore struct.
An RzBinFile struct does not contain much itself except for the RzBuffer corresponding to that file. Most of the important information is in the o field, which points to an RzBinObject struct.
An RzBinObject contains most of the information about a binary, including its symbols, entries, and sections.
It's possible to augment Rizin's existing binary format handling by modifying these bin objects from the SWIG bindings. It's also possible to create plugins in supported binding languages to add support for new formats.