This is a great little lubricated alloy steel glass cutter, perfect for cutting glass for fusing. It has a hardened alloy steel cutting wheel with a spring loaded block which controls the flow of the oil (so the oil only comes out when you press down). It also comes with a very handy filling pipette. You will need to get some oil though, but just some sewing machine oil will do which is cheap and easy to get hold of.
This has a very similar mechanism to a Toyo cutter.
To use you simply push down and score the glass (straight lines are by far the easiest), and then gently snap with your hands, and it should break at the line.