I plan on buy an iphone and I want to know if this one is a good one?

I want to purchase a iphone 4s 5th generation, but what does that mean? I seen another phone that said iphone 4s fourth generation, but it cost more than the 5th.why? Which is better?

I know there's a new iphone out but what is the difference and if you have a phone with 8 gb can you buy more or would you have to purchase a phone that has more gb.

Also if a phone is unlock does that mean you can get a plan from any cell phone company?

sorry I know nothing about phones.dial text and talk is all I know.

Iphone 5s & 5c are best apple smartphones. Click on the link below to see their features and buy them on amazon