A noun followed by は is used to establish the topic of a clause.
エンジニアです。
He/she is an engineer.
As we saw previously, in Japanese, the predicate is all you need to make a complete clause, as unlike English, the subject of the verb is not necessary. However, there may be times when you want to explicitly state what you are talking about. In this case, Japanese behaves a little differently to English in that a topic is used. A Japanese topic applies to the whole clause, whereas a subject only applies to the predicate.
