Matrixport is Bitmain's exchange.
Basically if you got money on the exchange, you can use it to buy Miners instantly thats pretty much it.
I went to check it out a while back, but wasn't really impressed
Sounds much like Amazon letting you buy
BTC to be used only for future purchases. They get to bank the fiat you send them and use in in typical Financial fashion -- use it to leverage other financial resources to make money on your deposit(s).