GE Update?

I've seen people talk about it updating... What does this mean and when does it happen?

once a day the grand exchange will update its prices it is "semi random" it is based on a very complex algrithim which has been cracked but not released to the public
and it can updated anywhere from 47 hours apart or 5 mins apart its all "random"
if an item has been bought out all day then it will go up its max 5% (assuming only 1 was bought the entire day)
the more that get sold the less it gos up
then less that buy the more it gos down

to sum it up simply: "geupdate" the prices are updating