Yes, (NH4)2CO3 is a salt. A salt is a compound that forms when an acid and a base neutralize each other. (NH4)2CO3 can form when ammonia, a weak base, reacts with carbonic acid, a weak acid. The reaction is:

2 NH3 + H2CO3 -> (NH4)2CO3 + H2O

Ammonia and carbonic acid are the parent base and acid of (NH4)2CO3.