Here is the yearly breakdown of John Buck's contract.

Buck passed his physical yesterday and the deal was completed, a day after the sides agreed to terms. He gets a $1.5 million signing bonus, $4.5 million next season and $6 million each in 2012 and 2013. Buck was a first-time All-Star this year, when he hit .281 with 20 homers and 66 RBIs for the Toronto Blue Jays.

I guess the advance (signing bonus) is for moving expenses.  Movers, deposits, walking around money...  things like that it.  Buck most definitely has a very straight forward contract.