Sudoku Training is part game, part reading material. For those who just want to get on and play, you can dive straight in with puzzles of four different settings; Easy, Medium, Difficult and Expert. Those who want to discover more about playing the game, meanwhile, can delve into the "Learn" area.
Learn is split into four main sections. General, Rules and History are merely short pieces of text that give you the basics on all three subjects. The former two aren't really anything different to what you'd find in a standard Sudoku game, while the History section is a nice, concise bit of info for you to digest.