Back during the early days of the PS3 and Xbox 360 console generation, the lack of backward compatibility became an issue. Gamers were unable to play their favorite games from the last generation on their shiny new consoles. This was a feature that turned out to be too big to solve in this generation but instead led to the rise of the HD remake.
A HD remake is a game that has been remade to take advantage of the high definition visuals that come with most modern game consoles. Due to the massive popularity of this, game publishers have continued to release older games on the new generations of consoles. The difference between a remake, remaster and a reboot can get confusing since they tend to be used for the same thing. A HD remake is generally a new build from the ground up rather than upgrading resolution from a past generation game.