Definition: A verb phrase is a group of related words that contains one or more helping verbs and a main verb.  For example....

Jim has been working on his science project.
The verb phrase is has been working.  Has and been are the helping verbs, and working is the main verb.

Sometimes the helping verbs are separated by other words, and thus one has to look carefully for the parts of the verb phrase.  For example....

Has Joan written her report yet?

The verb phrase is has written.  The helping verb is has and the main verb is written.  Note that the verb phrase is separated by the subject, Joan.  Sometimes you can find the verb phrase more easily in a question sentence by changing it to a statement.

Joan has written her report.  (Note that the verb phrase is now together.)
 

Gene will always do his work on time.
The verb phrase is will do.  Will is the helping verb and do is the main verb.  Notice that the word, always, is an adverb separating the verb phrase.  It is NOT part of the verb phrase.

Don't buy that present.
The verb phrase is do buy.  Do is the helping verb and buy in the main verb.  Note that n't (meaning "not") is not a part of the verb; it is an adverb, making the verb negative.