+0
Is there any relevant differences betweeb the two categories?

I know that phrases can idioms, too. But to the best of my knowledge, idioms don't necessarily

have to be phrases which have to be treated as adverbs, correct?
+0
Idioms are groups of words holding a different meaning than the words do severally. An idiom can be any part of speech.

Phrases are simply groups of words having some kind of conceptual adhesion; by some definitions, even clauses are phrases. They too can be any part of speech.
Comments  
Idioms are phrases with figurative meaning.
chivalryIs there any relevant differences betweeb the two categories?
I know that phrases can idioms, too. But to the best of my knowledge, idioms don't necessarily
have to be phrases which have to be treated as adverbs, correct?