Noun is the main part of a sentence and one of the most important pillars of English grammar. Noun is the name of thing, place or person in a sentence. A noun can further be classified into proper noun, common noun, collective noun and many more.
One thing to keep in mind is that as collective nouns represent clusters of people (usually two or more), it might not always use plural forms of verb. The form of verb (whether singular or plural) varies between different collective nouns. Some are used with singular verb while others are used with plural verb.
How to figure out which form of verb should be used with a particular collective noun? It all depends on the verb or action that is happening in the sentence. If everyone in the group of collective noun is behaving in a same way, singular verb is used. However, if the members of the collective noun are behaving differently or individually in the sentence, the collective noun is used with the plural form of verb.
Now consider another example;
The above two examples, both use the same collective noun committee in different ways. In the first example, the members of the committee all agreed about one thing and were on the same page, so the singular verb agrees is used in the sentence.