If you're thinking about a shortboard surfboard, you're thinking about high performance surfing. You're thinking about surfing in the critical part of the wave and going the fastest as the wave will push you. In riding a shortboard, what you do is you're going rail to rail, pumping the board rail to rail, gaining speed in and out of the critical part of the wave. And what helps you do that is the narrower nose helps you come up into the pocket of the wave and then the area here planes you. And then you have your tail, this one is a squash tail, which is the most common tail in shortboards. And basically, your squash tail gives you lift, and it gives you release when you're turning into the face of the wave.
In your basic shortboard, you have, your bottom contours are single concave to a double concave with V off the tail. This makes the water flow come down the bottom of the board and right through the fins. And shortboards are meant to be rail to rail surfing. You're always generating speed from rail to rail, pumping the board, and getting more and more speed out of the concaves.
Concaves will give you lift on the board. Whereas, V's will help the board come over on rail. This would be an intermediate to an expert surfer. You just don't stand up on them and cruise on them. You pump the rail on, you pump the water through the bottom of the board, and you get into the tight, critical part of the wave.
And that is, basically, your shortboard.