What's the name of this tool of Blender? That tool/mode where you have a background image and you can start modeling things, create meshes and etc. using that image as reference? 
Also: Can ANY image be used in this mode/tool?
I think there is no special mode for this. Once you have a background image added to the scene (Shift+A > Image > Background), create your first primitive in Object Mode, then switch to Edit Mode and start modifying and extruding your model based on the background image.