What are gradients in Canvas used for? What are their different types?

Gradients in canvas are used to fill rectangles, circles, lines etc.
The gradients in Canvas are of two types:
- createLinearGradient(x,y,x1,y1) – It creates a linear gradient
- createRadialGradient(x,y,r,x1,y1,r1) – It creates a radial/circular gradient