"technical friends" (which i believe was name given by the man who invented them, Ray Jardine). "Friends" is still the category name used by Wild Country, which i believe was the first shop to sell the devices.

more generically, i believe they are known as spring-loade cam devices (SLCD).

these simple devices transformed granite crack climbing from slow, rock-altering aid climbing that required pitons hammered into cracks to clean "free" (ie, no aid) climbing.

sure nuts and hexes were (and still are) available but they require some sort of constriction in the crack (change in the width) to hold them in place, which granite cracks often lack.