The different files of C

I'm trying to form a mental model of something that is never truly explained in any post or tutorial.

What is the purpose of the following files:

• .c
• .h
• .a
• .o

.c now I assume I could write the whole program in this one file but honestly I like making libraries so I guess my functions go somewhere else and are included in. But is that where the .h comes in?

As for .a and .o let's go, tell me more are there any more of the alphabet I should know?

.c .h .a .o .s seems like there a hidden meaning to c programming?