Differences about .a files and .o files (static libraries and objects).

[jacknpoe]

What the main differences about .a files and .o files (static libraries and objects), besides the fact a static library can link various object files?

How I can see what is inside a static library file? (not only the "published" objects like in "ar t" or "nm" commands, but the real structure)

And what is most easy? Decompile a object file, a static library or a executable?

[keskiverto]

From man ar

The GNU ar program creates, modifies, and extracts from archives. An archive is a single file holding a collection of other files in a structure that makes it possible to retrieve the original individual files (called members of the archive).

Could the .a be a mere archive of .o files?