Mac Forums

I was on sprints website today and i was thinking about going with the I Phone 4s or Samsung Galaxy. I was thinking about going with the I Phone 4s, and when i clicked on it, it said that it was originally $650 and i get $450 off for a 2 year agreement. what does the two year agreement meant? also I read online that you pay $50 a month for the I Phone, what is that for and do you pay that for the Galaxy?