I have invest my experience in BitOffer. And from my experiences thoughts, BitOffer’s Bitcoin trading includes spot trading, BTC Futures Trading, and BTC Options. 
1) Spot trading is trading between one digital currency to another digital currency. The direct object of buying and selling is the digital currency itself. 
2) The buying and selling objects of BTC Futures Trading are futures contracts. It is how many lots or lots of futures contracts are bought or sold. The purpose of BTC Futures Trading is to get profits from hedging to avoid price risk or investment. 
3) Bitcoin options is essentially Bitcoin derivatives, and they are also hedging tools based on spot. It is very friendly for investors with limited capital and is also a hedging tool based on spot.