PGSharp is a third-party application used for spoofing in Pokémon GO. It allows players to manipulate their GPS location to move around the game world without physically being there. However, it's important to note that the use of such third-party apps is against the terms of service of Pokémon GO and can result in penalties, including being banned from the game. Players should use caution and consider the risks before using any spoofing applications.