A Pin is essentially a code that can be redeemed for up to 3 months of Runescape membership, however it is usually sold in 1 month increments. It is normally obtained when you text a certain number, or call a number, you will be charged a certain amount. You can buy them secondhand on Sythe however.
Not sure. There are some methods of obtaining legit pins, however I will not mention them, as most of them I don't know myself.
