Also I looked into it and found that there used to be and sometimes is a concept called "standby ticket". Where is it used, and how does it compare with overbooking in terms of commitment to passengers?
Ah, standby. Now in the uk it is not really so common, unless you are travelling on a full fare ticket for the cabin you wish to travel in. The idea is this, you book for a certain flight, but your ticket can be used on any other flight on the same city pair or fare, if the flight has empty seats, on you go, if not you standby until flight closeout. As so few pax are willing to fork out for a full fare ticket versus a cheapy confirmed, we are back to overbooking again.
In the US it is possible to buy a revenue standby, I'll hand this over to others for other countries and their rules and regs regarding standby. Then you have the staff that travel on standby, they are on duty or leisure travel and this does occur all over the world. Standby passengers do not account for the booking figure on any flight, because in theory they do not exist until the door is closed and the final figures accounted for. Now does everybody get that? Good.
Overbooking works, it is very rare that you will see people being "bumped". We regularly over book by between 10 and 80 on our longhauls and still go with empty seats and accommodate staff standbys.