Hi and Welcome Stitcher
Bid groups are great if there are lots of the same/similar widgets on ebay that you are interested in. Someone a while ago used the Ink Cartridge example - there are always oodles of them available.
AS will bid on all the cartridges you put in your bid group and it will bid on cartridge after cartridge until it wins one(or however many you want) for the price that you are willing to pay. All the other cartridges in that bid group will be cancelled once it wins the number required.
As Rick said, in your normal my snipes folder - AS will bid on everything in there. If you have 6 catridges in there - you may well win 6 catridges.
Lexie