Multiple addresses in transaction I am a total noob, so this might be a stupid question. I was looking at this transaction, and saw multiple inputs and outputs. 

https://blockchain.info/tx/851e8c744494cd01070ca3723ec571137cc29558d1fd4b009bc81c3d75753540

What does this transaction mean? Who is sending to whom? Is this a multisig transaction? Why are there multiple receivers?
This is a normal transaction for an exchange paying out their users. The inputs are from user deposits and the outputs are for user payouts. It's very hard to know without a look at their database who owns which address, but this type of transaction is very common for large services like exchanges.

The reason there are so many inputs and outputs is that it's a lot cheaper for the exchange to send out 1 big transaction instead of many little ones.