Nouns and the nominative

Every German noun has a gender: masculine (der), feminine (die), or neuter (das). You can tell the gender from the article.

The definite article is der, die, or das. The indefinite article is ein, eine, or ein. In the plural, the definite article is always die: die Kinder.

The form here is the nominative. That's the case for the subject in a sentence — the person or thing that does something: Der Mann liest.