dumb rail pass question

[pinknic38]

Okay this is probably a lame question but I've never needed a rail pass before and now I do so please bear with me.

I've got the 6 day Germany pass and when I look online on raileurope.com at the schedule of the trains, it's like 12 bucks to make a reservation, if I have a rail pass... do I need to make a reservation for city-to-city trains that are not overnight or anything? And is the 12 bucks just for the reservation or will I get on the train with my rail pass and be asked for 12 bucks there?

I don't get it... I pay this $ for a damn rail pass then you still have to pay for the trains! It doesn't make sense...