Pointillism is an original form of art created by George Seurat. Pointillism is a bunch of tiny dots formed together to make a picture. Why we use pointillism instead of using a paintbrush and just painting is because pointillism is brighter and the other kinds of paintings can be dull. When two colors are next to each other, your eye mixes them and that is called optical mixing. Using optical mixing instead of physically mixing can make a brighter picture.
Pointillism was a relatively short lived movement, although it did influence Fauvism, in particular Paul Gaugin, as well as Divisionism, a similar movement which relied on the use of primary colors. And if you look closely at your TV screen you will see the same technique is used there to create an overall effect.