A Breadboard is a handy peice of kit, used for electronic prototyping. Because it requires no soldering, and the components are simply pushed into position, you can keep rebuilding aver and over again!
Here is a Breadboard :) just for those of you who didn't know ;)
Here you can see the internal connections of a breadboard.
When using a Breadboard with a Raspberry Pi, you can either use a breakout board, or use female to male jumper leads to connect the Breadboard to the GPIO.
Raspberry Pi with breadboard using a breakout board
Raspberry Pi with breadboard using female-male jumper leads