Drop sets/ shock training

[canibalistic_js]

I have heard this tearm a lot in BB books. I wanted to know what exactly conbstitutes as "drop sets" and shock training. Everytime I go into the gym I usually train that body part until failure then I train the secondary muscle group to fatigue but I'm trying to figure out what this stuff is.

[antihero]

this explains it well

http://www.dolfzine.com/page587.htm