What is a subject complement?

The subject complement is the fallowing a verb which describes the subject.

In grammar, a subject complement or predicative of the subject is a predicative expression that follows a linking verb and that complements the subject of the sentence by either renaming it or describing it. It completes the meaning of the subject.

Explanation:

Common examples are to be, to become, to appear, to feel, to look, to smell, and to taste.