Hi, I did few things with XNA in 2D and I wanted to try programming 3D...

I started with the "getting started" tutorial displayed in the xna help... but there are a lot of terminology not explained, and I don't know where I can find definitions...

For example, in "Displaying the Model on the screen" how you can create your own model and what's the meaning of the model's code is not explained, or how and why the matrix are used or what's a "mesh", neither.

Where I can find this sort of information?

Thanks!

The matrices are used for transformation in 3D space. An article that exaplains the different coordinate systems that are used in a 3D application can be found here
More info on matrices here
Riemer also has a few tutorials, and some articles related to Matrices: 1 2 3

a Model = a collection of meshes
Each mesh in a model can be moved independently of the others, by means of bones.
A mesh is a collection of meshparts, which share a vertex buffer and an indexbuffer
Each meshpart is a set of primitives that share the same material (Effect)

thanks! now is a bit clearer ^^