The New Wave of British Heavy Metal (often abbreviated to NWOBHM) was a phrase first coined by Sounds metal editor
Geoff Barton. The phrase referred to heavy metal
bands who kicked out all of the
blues, sped up the tempo, and toughened up the
sound, leaving just a mean, tough, fast, hard metallic core. This style was pure metal, made for metal fans, it had more good riffs then ever before.
The most important artists of the style are:
Iron Maiden, Judas Priest, Motörhead, Diamond Head, Def Leppard, Angel Witch, Raven, Samson and Saxon.
Other bands, like Metallica, are greatly inspired by those bands too, as evidence you need to look no further then the cover album Garage, Inc, most of the songs in that album are covers of NWOBHM bands.
NWOBHM originated in the late 70's. It takes its roots from British metal bands like Led Zeppelin and Black Sabbath, it is the source of modern metal styles like : Speed Metal, Heavy Metal and Thrash.