So I'm taking embedded systems subject in my masters course. They have mixed this subject's content with electrical engineering and I'm a computer science graduate. Everything was perfect until I reached to GPIO board.
Wtf is this shit?
Why it has so many holes and what are they for?
What I'm supposed to do with it?
What is ground? Transistor?
Why I'm connecting to two pins only instead of the 4 pins of a button?

Thanks to pi4j i think i will pass the subject!

GPIO stands for general purpose input/output, and usually means that they are programmable pins (you can use, generally as 0-5v or 0-3.3v, ymmv

You connect stuff to them, and you can program the board to do things, like reading some 4-20ma current or close a relais

Trasistor is a sort of (electronic engineers here may want to bear with me) electronic switches that can be assembled in logic gates.
Ground is just what you choose to be the neutral "0" of your system.

You connect only 2 of the 4 pins of a switch usually because switches can support multiple i/o (and to recycle the same base of a commutator)

@-eth Thanks for the reply and the info.