Blur

There are many different types of blur. As VFX artists we often care about Gaussian blurs for our textures, motion blur for our particles and radial blur for our post fx.

All blurs have the same base. They take one pixel and smear it over other based on some rules. In some cases it's to convey motion captured by a camera. Sometimes it's to soften up a texture. Blur is our friend, unless you try to do brute force it in a shader. Then the performance gods will strike you down.

Further reading: https://en.wikipedia.org/wiki/Gaussian_blur