This is the typical layout for a Solana program as it grows in size and begins to require multiple Rust files. You'll notice a lot of the programs in the Solana Program Library follow this format.
Note: You can structure your Rust
srcfolder however you wish - provided you follow Cargo's repository structure standards. You don't have to follow this pattern, but it's here so you can recognize other programs, too.
You can see that the structure for a native repository is very similar to that of the anchor repository. The only difference is the inclusion of a processor.rs in the native setup - one of the many things Anchor abstracts away for you!