A confusion in pre-define in TM4C c programing

Hello, Everybody. 

in TM4C c programming, There is "IntEnable( INT_TIMER0A )" operation,

Where, INT_TIMER0A is pre-defined like this：

#define INT_TIMER0A    INT_CONCAT( INT_TIMER0A_,  INT_DEVICE_CLASS)

and INT_CONCAT is defined as：

#define INT_CONCAT(intname, class)     INT_RESOLVE(intname, class)

and

#define INT_RESOLVE(intname, class)     intname##BLIZZARD

I just can not understand what is the function and purpose of "class" in these code. "class" is parameter in the definition, but why it does not function anything here? at least it seem so.

Thank you !