Bitcoin is a currency which is internet based i.e. it is stored or spent on internet only.
To be qualified as money, there are some characterstics to be fulfilled like
Durability
Portability
Divisibility
Uniformity
Limited Supply
Acceptbility
One good thing about bitcoin is that once the transaction is complete, they cannot be reversed back to the original owner who send you the bitcoins. That is why most majority of people uses bitcoin and NOT paypal.
Regards
Buddie