How to Create a Normal Map? And etc

Hi. Total ****** here.
Explain please could you?
What’s a normal map, diffuse map(etc), why do I need them, how do I create them, how do I create a material of them.

For example I have a low-poly statue model and want to apply a texture that contains a normal map. What should I do? What goes first? Texture, normal map some etc map? Cheers mate