What is usefulness of linear and radial gradients

Answer 1

CSS Gradients

CSS gradients let you display smooth transitions between two or more specified colors.

CSS defines three types of gradients:

Linear Gradients (goes down/up/left/right/diagonally)
Radial Gradients (defined by their center)
Conic Gradients (rotated around a center point)

https://www.w3schools.com/css/css3_gradients.asp
https://www.w3schools.com/css/css3_gradients_radial.asp
https://www.w3schools.com/css/css3_gradients_conic.asp