F. Why do verbs have different forms?

The verbжить [to live] appears in two forms in this lesson: (он/она) живётand (они) живут. Verbs in Russian, as in English, agree with their subjects in terms of person (I, you, he/she, we, they) and number (He lives, vs They live.). The two forms indicated here are for a singular subject and a plural subject, respectively.

Он живёт в Москве.Не lives in Moscow.
Она живёт в Киеве.She lives in Kiev.
Они живут в Америке.They live in America.
Кто живёт в Украине?Who lives in Ukraine?
В Украине живут украинцы.Ukrainians live in Ukraine.