Artisan tools use an intuitive paint and sculpting-based interface to accomplish a variety of modeling, animation, rendering, and effects tasks and deliver high quality and otherwise complex results in minimal time.
See also How Artisan brush tools work.
There are several Artisan brush tools that all work like paint brushes. Typically, you create your model in Maya, then paint over it with these tools to detail and modify it. You can use your graphics tablet and stylus for greater control when you paint.
You can access some of these tools by pressing down the right mouse button over an object and selecting from its Paint pop-up menu. Or, access them from their respective menu items as described in Tools that use Artisan.