I am using Assimp asset importer (http://assimp.sourceforge.net/lib_html/index.html) to parse 3d models.

So far, I've simply pulled out the normal vectors which are defined for each vertex in my meshes. Yet I have also found various tutorials on normal maps...

As I understand it for normal maps, the normal vectors are stored in each texel of a normal map, and you pull these out of the normal texture in the shader.

Why is there two ways to get the normals, which one is considered best-practice and why?