The artist is using a cobblestone texture for this tutorial, which you can get for free here.

It is worth noting that basic knowledge of Photoshop, any 3D app, and the high poly to low poly workflow is required to understand the guide.

The artist uses software such as Agisoft Photoscan, Photoshop and ZBrush. You can use any similar tools. For example, you can get started with Autodesk 123D Catch for free.