I wanted to make or find a shader like this for the game that I am planning on making. 
How do I exactly do it or what is this called?
A material has a couple parts to it, you can have colors, textures, normal maps, you name it. One of the used components is the shader. The shader is responsible for how light is processed and how the reflection work and all that stuff. What you are looking for reminds me the most of a “Toon Shader”. This will give a cartoon look with sometimes a black border around the object. Also found something called “Cel Shading” which might be something you are looking for, but you are definitely looking for shaders and not so much materials.