PB Blaster is a penetrating oil, like Liquid Wrench and such. We use it where I work, and like Jim, I tend to use it to clean greasy and sludgy press parts before I use anything else to clean with. It cuts through grease and grime very well, but remember that it is an oil, so to get things really clean, a regular detergent type cleaner should be used next. If you are not worried about getting things to that level of "clean" then just let it be. It doesn't seem to leave any kind of residue behind, and on machine parts, you might want a little oil film left behind. I don't know what PB stands for either, but can guess that the P stands for "penetrating".
Type at you later,
Dan McEntee