serve something on someone
to officially deliver something, such as a subpoena, to someone. A prosecuting attorney served the subpoena on Max. The document was served on the plaintiff by a sheriff's deputy.
serve on something
to carry out one's duty or responsibility on something, such as a committee or a board. Will you be able to serve on this committee next year also? Sarah refused to serve on the committee again.
To serve a term of duty as a member of some official body: Have you ever served on a jury before?