What does 'interim bout' mean?

In refering to world title bouts, a fight for the interm championship means:

A champion (for instance a WBA champion) hasn't defended his title due to injury, so two contenders fight for the "interm" belt, meaning that whoever wins (the interm champion) has to fight the real champion when the "real" champion is fit and ready for action.

Basically, it's just a money making think from the alphabet boys.