What is this "blur" or drawing called and how to do it in CSS?

Question

css

Thanks for answers!

Answer 1

Background blur
https://codepen.io/ariona/pen/geFIK

Answer 2

background picture is

Answer 3

Through background and gradients, but simpler than a picture.

Answer 4

This is an image.
In Photoshop, apply a Gaussian Blur to the image + you can also add Motion Blur

Answer 5

At first glance, the usual linear gradient.

Answer 6

Either with a simple picture, or in svg if you need to recolor it later in css

Answer 7

multiple gradients with translucency