Copula(r) verbs are used to associate an attribute or obligatory adverbial with the subject of the clause,

i.e. they link the subject and the subject complement (hence they are sometimes called "linking verbs"):

She is the new president.

or locate the subject in time or space:

I was at the cinema.

Depending on the context, some verbs - like go, grow, and come - can function as either a copular verb or a regular transitive/intransitive verb. Compare

My dream has come true. (copular)

Will you come to my party? (intransitive)