MAC Pigments are basically highly concentrated loose color powders that come in different finishes: Matte, Metallic and Frost. They are a dream to blend, do not streak or cake and last forever. And since they go on super pigmented, you only need a teeny bit each time. You can also mix them together to get the color you want.
Another awesome thing about pigments is that they are multi-purpose. Below are some of the ways you can use them: