There are a series of default toon shaders available in the Toon menu, all designed to work with simple lighting. When you assign a toon shader to selected geometry, a shader node is created. You can edit the shader in the Attribute Editor. All of the toon shaders, except the Solid Color shader, are based on the Ramp shader. On a Ramp shader you can create multiple indices (tones); for more information, see Ramp Shader in the Shading guide. By turning on High Quality Rendering, you can get an accurate preview in the scene view of what the toon shaders will look like when rendered.