So, what the heck are Active/Active and Active/Passive Storage Arrays?
And what is the difference between them?

In an active/active storage system, there are multiple paths to a LUN. All of these paths are active simultaneously. However, a preferred path policy is used. The failover occurs when a NO_CONNECT is received.

In an active/passive storage system, there is only one active path to a LUN. All of the other paths are not active and are in standby mode with respect to that LUN.
The failover occurs when a NOT_READY, ILLEGAL_REQUEST or NO_CONNECT is received.

The major difference is that, in an active/active storage system, when the preferred path has come back online, after the failover, the LUN’s are failed back over to the preferred path automatically. In the active/passive storage system the path where the LUN’s have failed over to is used even when the original path has become active.