Morphs, the actual forms used to realize morphemes.
A morph is the phonetic realization of a morpheme. The real form of the morpheme, the actual utterance of the morpheme.
Example:
cats bus
[cat + (-s)] [bus + (-es)]
Allomorphs, any of the different forms of a morpheme.
Allomorph is phonologically distinct variants of the same morpheme.
Different realization, manifestation of the same morpheme.
They vary in shape or pronunciation according to their condition of use.
They are a class of morphs which are semantically identical.