Like Ren has mentioned, an arpeggio is just the notes of a chord, played one at a time, in order. It can be seen in a number of different types of playing.. a couple of obvious ones would be "sweep picking" and "finger tapping".

Here's some stuff on Arpeggio shapes (theory)
http://www.guitartricks.com/tutorial.php?input=31

Here's some stuff on sweep picking (practical)
http://www.guitartricks.com/tutorial.php?input=408