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.