they're for item drop tables (trigger based or otherwise). for example, in an item drop table you can have it drop a random [item type] of level [whatever] the more powerful items are grouped in higher levels so you know more or less what you're getting when you use that function or whatever you feel like calling it.
sure no problem. i think i actually picked up the random items of level from a map instead of figuring it out for myself but i'm always ready to pass on knowledge, mine or someone else's (provided that the someone else lets me)