what is the difference between collective and compound noun ??

A collective noun is a noun that states a group of persons or things and are considered to be as 'one whole'. For example, a crowd, a flock of sheep, a herd of cattle, an army, the police etc.

On the other hand, a compound noun is a noun that is formed by combining two or more nouns. For example, daughter-in-law, passer-by, ice-cream etc.