what is gradient in css code example

Example 1: css horizontal linear gradient

background: linear-gradient(to left, red, blue);

Example 2: css horizontal gradient background color

.foo {
	background-image: linear-gradient(red, blue);
}

Example 3: css gradient

Here a codePen with cool gradient animations:
https://codepen.io/DevLorenzo/pen/ExgpvJM