A static library is usually identified by a .a (for "archive") suffix (e.g. libc.a). The library contains the modules you want to include in your program and is formatted as a collection of ELF object modules that the linker can then extract (as required by your program) and bind with your program at link time.
This "binding" operation literally copies the object module from the library and incorporates it into your "finished" executable. The major advantage of this approach is that when the executable is created, it's entirely self-sufficient — it doesn't require any other object modules to be present on the target system. This advantage is usually outweighed by two principal disadvantages, however: