Find a problematic ROM, such as a PSP game that requires a specific firmware version. Rename the file from game.iso to game.nexus2 . Double-click it. If installed correctly, the Nexus Rom Extension 2 will read the file header, launch your default emulator, and apply the necessary patches instantaneously.
"Nexus ROM Extension 2" most likely refers to the ROM+ Extension 2 reFX Nexus nexus rom extension 2