What's The Difference between all these Lens?!

Hey guys, I'm new to all this Photography stuff.
I'm planning on getting a Nikon D3200, With the Lens… The 18-55mm one… I think.I'm not stupid, I just find all these different millimeters with all these different lenses confusing. Why are there different lenses? What does a 14-25mm lens do different than a Kit 18-55mm lens? What does that little F mean? What does 1.8 mean? Whats the difference. Why do you need more than two lens? I dont really understand what it does differently. I am getting this Camera MOSTLY for video shooting, So does the Lens Mostly matter for photos? Or does it do something to the videos as well?
Since i am mostly getting a DSLR for Videos, What would you guys recommend? A Canon 600D or D3200? You guys can answer the camera Question last, please help me understand this whole lens thing.

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