The 9×19mm Parabellum (Parabellum coming from the Latin phrase "si vis pacem, para bellum", roughly meaning "if you seek peace, prepare for war"), also known as the 9mm Luger, is a widely used German pistol round. It was designed by Georg Luger and introduced in 1902 by German manufacturer DWM (Deutsche Waffen und Munitionsfabriken). In its standard loading, it is referred to as 9mm Luger, and is currently one of the most popular handgun cartridges in the world, in use with several military forces and many law enforcement agencies.
9mm Luger - The standard loading in 9mm. Can be found weighing anywhere from 92 grains to 147 grains.
9mm NATO - Fires at a slightly higher pressure than the standard 9mm Luger. It is denoted by the NATO insignia on the case rim, and uses red sealant on the primer. The bullet weighs in at 124 grains.
9mm - Loaded to C.I.P. spec. By western definition, this ammunition is loaded to near +P pressures.
9mm +P and 9mm +P+ - overpressure variants of the 9×19mm cartridge, fires at higher pressures than the SAAMI-spec 9mm Luger. These are usually found as jacketed hollow point (JHP) rounds.
7N21 and 7N31 Armor Piercing Steel Core +P+ - Armor-piercing variations that are the new military, police, and FSB-issue rounds of the Russian Federation. Firearms such as the GSh-18 pistol and PP-2000personal defense weapon were designed to handle this overpressure cartridge.