What's the difference between the Iphone 4 and the newest version Iphone 6?

I ordered this one just recently…

http://www.amazon.com/Apple-iPhone-8GB-Unlocked--Black/dp/B005ZD6WQS/ref=sr_1_2?s=wireless&ie=UTF8&qid=1447247815&sr=1-2&keywords=Apple+iPhone+4+8GB+Unlocked-+Black

I mean I wanted to get the cheapest Iphone they had available since I can't afford the much newer, expensive ones they make nowadays. So will I still get mostly everything I want on this old one and what's the difference between this older model compared against the newest one? Will I really be getting my money's worth? How long ago was the version I'm getting released? I'm just curious. Please just tell me what I'll be getting and what I won't be getting.

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