There is a little confusion over the term 'community' as it is usually used to describe fish (e.g. 'community fish') that can be kept together in a 'community aquarium' where all the inhabitants will get along.
This 'labeling' system, which is often used in books and on labels in fish shops has a few flaws, as not all fish labeled as 'community fish' will get along, defeating the point of the term being used.
The problem occurs because even some fish that are generally peaceful and trouble-free may squabble with other normally peaceful fish, but it is difficult to exclude them from the 'community' label because in the majority of cases they would not cause difficulty.
As an example the Red-eye tetra is a peaceful, active shoaling fish and so is the popular Guppy. Both these fish can be classed as good community fish but together; the red-eye tetras will nip/bite at the guppies.
Because of these occasional situations the term 'community fish' should be used as a rough guide, indicating that the fish in question will in the majority of cases, be a peaceful fish. Using the term for a 'community aquarium' however, is a different matter.
A community aquarium is simply an aquarium containing a mixture of fishes that make good tankmates. This does not mean they can be mixed with all peaceful fishes, just that the fish in that particular mixture make a good community of fish. For instance, an aquarium stocked with Lake Malawi cichlids could be described as a 'rift lake community aquarium', or one stocked with fish from South America could be described as a 'South-American community aquarium'. The fish within each of these two communities will get along fine with the other fish in the tank, but if the two communities were mixed together there would be major conflicts of interest both in terms of the fishes behaviors and the water conditions the fish require.