A "copula" is a word used to link a subject and a predicate in a sentence. Common examples include "is", "am", "are", and "be".

Accordingly, an example of such in a sentence would be:

"I am glad to see you."

or

"The group is excited to have been accepted."

In my personal experience, in English 101/102, simple or cliche use of copula is discouraged. Action verbs, instead, can be used in their place.

Examples of sentence avoiding the standard use of copula:

"Seeing you fills me with glee."

or

"The group revels in the news of your acceptance."

Bottom Line: You use copula to link a subject with other subjects, verbs, adjectives, etc. In writing it may be beneficial to use actions to connect the sentence. They too are copula, it just sounds better.

1. Subject

2. Predicate

3. copula