Longboard shape questions

Hi,
I'm reading and watching and browsing surf mags, pics, videos and shops.. just to enjoy the beauty of the surfboards and the skills of the riders. (still no waves here..
)
But as I don't know much about shapes, few questions rise in my mind:
-how a rocket nose influence the ride and/or behaviour of the board?
-does it have something to do with nose ride?
-what about rocket tail?
-When you say parallel rails, what do you really mean? Symmetric? This may be a stupid question but I don't find any single board with parallel rails!
This is the closest to parallel I found: http://www.blackapachesurfboards.com.au ... logs-pigs/
I'm speaking about the first, green board. And yet, it has less then 1/3 of the length parallel.
And so: how about parallel rails? what they make you do better? Why you'd want them?
-What happen if I move the central big fin forward?
I know they are a lot of questions and they require a lot to answer, but if someone can put down just a general idea of how this things work it would be very helpful, also regarding my future next board!
Thank you.
I'm reading and watching and browsing surf mags, pics, videos and shops.. just to enjoy the beauty of the surfboards and the skills of the riders. (still no waves here..

But as I don't know much about shapes, few questions rise in my mind:
-how a rocket nose influence the ride and/or behaviour of the board?
-does it have something to do with nose ride?
-what about rocket tail?
-When you say parallel rails, what do you really mean? Symmetric? This may be a stupid question but I don't find any single board with parallel rails!
This is the closest to parallel I found: http://www.blackapachesurfboards.com.au ... logs-pigs/
I'm speaking about the first, green board. And yet, it has less then 1/3 of the length parallel.
And so: how about parallel rails? what they make you do better? Why you'd want them?
-What happen if I move the central big fin forward?
I know they are a lot of questions and they require a lot to answer, but if someone can put down just a general idea of how this things work it would be very helpful, also regarding my future next board!
Thank you.