Microsoft is hinting that additional balancing algorithms may be coming in the future. When a queued component calls a method, that call is sent over a message queue to the actual component. The caller returns as soon as the message has been successfully written to the queue. The actual component then reads the message and processes the method. The caller does not wait for any response and the actual component cannot return any response to the caller.
All parameters are input-only since no values can be returned.
MSMQ is rich in features, so much so that a separate column would be needed to review them. I urge you to investigate MSMQ on your own. No matter how much speed a database cranks out, it never seems like enough. The cache can be up to 3 GB in size. There is a background thread that will update database writes back to the primary, disk-based database.