What is the difference between struct and typedef struct in C?

Basically struct is used to define a structure. But when we want to use it we have to use the struct keyword in C. If we use the typedef keyword, then a new name, we can use the struct by that name, without writing the struct keyword .

A struct in the C programming language (and many derivatives) is a composite data type (or record) declaration that defines a physically grouped list of variables under one name in a block of memory, allowing the different variables to be accessed via a single pointer or by the struct declared name which returns the …

The _t usually wraps an opaque type definition . GCC merely add names that end with _t to the reserved namespace you may not use, to avoid conflicts with future versions of Standard C and POSIX (GNU C library manual).