一个完整而正确的句子里只能有一个谓语，另一个或其他个动词就要变换形式成为非谓语动词。

I like playing football.

（like是谓语，playing是非谓语动词）

非谓语动词有三种形式：to do、doing 、done

to do表将来，表目的

I want to go fishing.

To get a great grade I try my best.

doing表进行表主动

I am reading books.

I saw a girl standing here.

done表完成，表被动

I have done my homework.

Enjoying music makes me feel relaxed.