It is basically implicit manual memory management. You make sure that your ownership is properly accounted for and it will then properly manage the memory they use. Unlike in GC languages, you pretty much have to understand everything about how your resources are managed, even in the API design phase.

Is reference counting not implicit manual memory management as well?

No! Reference counting is dynamic tracking of object lifetimes. If reference counting is implicit manual memory management, then so is tracing GC!

Manual means "a thing operated or done by hand rather than automatically or electronically, in particular." It is very strange to me that you've decided the manual means: non-dynamic tracking of object lifetimes.

Garbage collector frees objects when there are no more references to them. It thus does automatic memory management.

Borrow checker on the other hand doesn't alter lifetimes of objects, instead it doesn't allow you to keep references to things that were destroyed. I.e. it doesn't manage memory.

Sure, but I was talking about Rust's ownership system which certainly does alter the lifetime of objects. Rust automatically frees objects when the owner scope ends.