But that's only for when it's at your house, or some other place with wi-fi, so it doesn't have to use your Sprint data... thingy... all the time, right?
Correct - those are other WiFi networks in range of your phone. As you move around town you'll see dozens of networks, some open, some requiring passwords.
Yes, you can skip setting up WiFi if you don't have WiFi in your house. When you visit a location with WiFi, you can easily set it up there - many coffee shops, fast food places, offices and bars offer WiFi for faster data use.
I have recieved and activated my sprint iphone4s, I am now setting it up using onscreen setup menus. I am asked to choose a network from a list: "Blackmon", "Mamamio", and "Other".... Any selection requires a password to be entered. My question is, what are those networks? Someone nearby with a wireless router? ( I think probably..) Are they sprint or iphone networks? ( I think probably not...) I do not have a wireless server/ network of my own handy to sign into. Can I skip it untill later? Any info or help on this step of the setup? Thanks!