What is the structure of libc.so.6 time.c

Okay, I give up. I can't read C for my life!

1. What is the structure of time_t below?

   /usr/include/bits/types/time_t.h

   #ifndef __time_t_defined  #define __time_t_defined 1    #include <bits/types.h>    /* Returned by `time'.  */  typedef __time_t time_t;