Posterization

Posterization is when a picture looks like it's made up of blocks of colors instead of smooth transitions. Imagine you have a photo of a rainbow that goes from red to orange to yellow to green to blue to purple. If you posterize that photo, it would look like it only had a few blocks of color instead of a smooth transition from color to color. So instead of seeing all the different shades of orange between red and yellow, you might only see three or four different shades, making the colors look like they go from red to a bright orange, then to a darker, more muted orange, and finally to yellow.

Think of it like painting with crayons. If you color a picture with one color, it looks smooth and consistent. But if you color the same picture with different colors that don't blend well together, it might look like it's made up of blocks of color instead of being smooth.

Posterization can be used as a stylistic choice in art, or it can happen accidentally when editing photos. Sometimes it can be a good thing, but other times it can make the picture look like it was made in a rush or by someone who didn't know how to blend colors together properly.