Why we use curve Animation?

Can any one describe me . why we use curve in any character Animation ?

It Help to move born at other location ? (Change Born Location) or stretch any born

Curves can be used in many instances, mainly as a means to provide a value input that changes over time. For example, in the case of a character, a curve could be used to create a floating visual by using the likes of a sine curve as an input to the character’s vertical location. making them bob up and down… examples are endless. But generally, it is a means to easily and graphically control a value over time.

How can I learn about that

You have any Deep Tutorial link to understand or learn this topic properly
So It’s so help full for me