Pot equity is basically the percentage of the pot which you are entitled to, and the % of times you would win the hand if it were played out a very large number of times.
E.g.
You have AA vs KK all in preflop.
At this stage AA has 80% pot equity, KK has 20% pot equity
Download a program called PokerStove (
www.pokerstove.com). You can input hands and board cards and it will calculate pot equity for you.
Let me know if this explanation is unclear.