Me neither but here is the answer acording to AVG.
What is Rescue Disc of AVG Anti-Virus
Rescue Disc of AVG Anti-Virus is a special floppy disk(s) on which the most important system areas of your computer are saved. The contents of Partition table, Boot sector and other internal data are stored here. These areas are often targets of virus attack and this damage could cause a malfunction of your computer or Operating system ? for example, your computer will not start.
Reparation of such damaged system areas could be very complicated. But if you have created Rescue Disc, you can do it by easy and safe way.
With a backup copy of system areas on Rescue Disc, it also stores a special program, AVG-SOS, intended to service operations.