From what I understand, setting up a fan as a pusher fan, you put it in front of the radiator and make it blow towards the engine bay. "Pusher" is referring to the fan pushing the air through the radiator.

A puller fan is what they do stock. The fan is placed behind the radiator and blows toward the engine, thus pulling the air through the radiator.

A lot of the people who end up setting up their fans as pusher fans do it to allow for more clearance for their turbo kits...if you look at the space between your stock header and the radiator fans, there isn't much room for expansion, so people sometimes put the fans on the opposite side of the radiator to allow the turbo manifold and turbo to fit in there more easily. Alternatives include getting slim fans (if the turbo setup would even allow for that, space-wise), or just not having a fan there in the first place...not recommended for an everyday driver, especially if you live in a hotter climate.