Whats is the diffrence between AGP and PCi Express Graphics cards?

i seen different types of graphics cards AGP DDR, AGP i think there the same and PCI Express i got a fairly old pc about 4 -2 year old HP with an Integrated 64mb intel graphics chirpiest which one of these cards do i need to upgrade it what fitting is it i need a 128mb card to run the new football manager 2009 its for my mate