A group of cats is referred to as a clowder or a glaring. An unneutered male cat is called a tom (or a gib, if neutered) and an unneutered female cat is called a queen.
Five Good Reasons for Having Your Cat Neutered
Reduces fighting, injury and noise
Reduces spraying and smelling
Much less likely to wander and get lost
Safer from diseases like feline AIDS, mammary tumours and feline leukaemia