Bitcoin is a virtual currency that is very much in hype this year and is actually a concept that is based steadfastly on mathematics as well as financial buoyancy. It is basically a secret number that is passed using cryptography from one person to another.
Peercoin as known as PPcoin was built on the hopes of improving on the Bitcoin system. It combined the systems of proof of stake as well as work thereby beinging in a change in the entire system of virtual currencies.
Both Bitcoin and Peercoin have a lot in common but are quite different too. Where Bitcoin has a supply rate of 21 million coinsusing the hashing algorithm SHA256D, Peercoin has no such hard limit and uses the hashing algorithm SHA256.