The terminology of mixers is confusing because each manufacturer seems to have their own name for each function. Groups, subgroups, and submasters all refer to the same kind of module for instance.
 The drawings illustrate a mixer that is no longer made. They still are typical though.
This button might be labeled MIX, STEREO, or just R-L.
Yes, the input module has an output! Mixing consoles are easier to understand if you think of each module as a seperate device.
Be sure to check whether the signal leaves from the tip and returns on the ring of the plug, or vice versa. Different brands of mixer differ on this.
A pressed solo button on an unused input will shut the monitor speakers off. I have seen this feature lead to thousands of dollars worth of damage. ("Well, I didn't hear anything, so I turned all the faders up, then I noticed the solo was pushed.")
On many mixers, "normal" also known as unity gain, is 7.