A sentence refers to the pair of words which is complete in itself. In other words, a sentence contains a subject and a predicate or it may contain a main clause and one or more subordinate clauses to convey a command, exclamation, question or statement.
A predicate is a part of a sentence which contains a verb and tells something about a subject.
Hence, in the above sentence predicate is "See big yellow ones."
wherein, 'see' is a verb.