[nomadtla]

[ QUOTE ]
What does this mean exactly?

" I found myself sitting at a lot of 18/8 tables instead of 25/4."

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the two #'s x/x represtent a players VPIP=voulentary put $ in pot (or % of hands when they put money in the pot that they don't have to preflop - this is a judge of looseness), and their PFR=Preflop Raises (or % of hands they raise preflop - this is a judge of agressiveness)
All these stats are calculated by Poker Tracker

So a 25/4 plays a little loose and pretty passively
While and 18/8 is in less pots but more agressive when their in, which is a more optimal way to play