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