AP2.5 sector was put into the games as an anti piracy method.
It involved a challenge table (in the console, the dae.bin) that send a challenge to the DVD drive, the DVD drive then went over the AP2.5 sector and responded with a response, the console then verified it and the game got booted.
If the response was faulty the console would halt booting and flag your security data with an AP 2.5 trigger flag.
However, this AP method was severely flawed as stock consoles and legit games with heavy scratches also failed AP.
In short, it's just best to patch every game you have and don't scratch legit games (nor backups)
As for a Wiki...
No not really.
There's one on the 360's hardware similar to Wiibrew, but a piracy related wiki for the 360... nope.
It involved a challenge table (in the console, the dae.bin) that send a challenge to the DVD drive, the DVD drive then went over the AP2.5 sector and responded with a response, the console then verified it and the game got booted.
If the response was faulty the console would halt booting and flag your security data with an AP 2.5 trigger flag.
However, this AP method was severely flawed as stock consoles and legit games with heavy scratches also failed AP.
In short, it's just best to patch every game you have and don't scratch legit games (nor backups)
As for a Wiki...
No not really.
There's one on the 360's hardware similar to Wiibrew, but a piracy related wiki for the 360... nope.