Mesh information explained.

I can create meshes from scratch, unity basically gives you all you need. However I find it difficult to texture and such, I don't quite understand all the elements of a mesh. I tried to google this information, but nothing specific really came up. Also I just want to be clear, that I don't want to be told how to texture what I make. I want to understand what I am doing, so I can do it myself.

My question is can anyone explain the elements (what exactly are normals, tangents etc..) or point me in the direction of a good resource to get all this information? Preferably one source for all of the information (usually keeps things more consistent making it easier to understand.)

Thanks in advance.