Camera lens for portraits

Quick question about a camera lens for my NIKON D3100. I have a 18-55mm lens on it and want another one that will be good for portraits, I was thinking maybe the 35mm one but I was looking at the numbers and if I just turn my lens to 35 is that like the same thing? Or will the pictures look different with a 35mm?

Advice/tips anything will be appreciated!

If you adjust your zoom to 35mm then yes, the field of view will be exactly the same as with a 35mm prime lens. What will be different is that a prime tends to have better optical quality than a zoom (not always true though, especially for 'pro' zooms) and you will be able to achieve a wider aperture (the 35mm is a f1.8 lens, your 18-55mm will be achieve f4.5 or thereabouts as the widest aperture at 35mm).

A good portrait lens to use is the 50mm f1.8 - also one of Nikon's cheapest (& sharpest) lenses.

35mm is a little too wide for portrait, even with the 'crop factor' of your camera, it will distort features particularly if used close to the subject, exaggerating long chins and noses.

a 50mm f1.4 or f1.8 is normally considered a better proposition. On your camera it will be a 75mm which is ideal for portrait. The wide aperture means you can get those 'selective focus' shots where the background is blurred, but the subject is sharp.

My personal preference is even longer focal length than that, I tend to use a 70 - 200 f2.8, but I like to work further from my subject, it really is down to personal preference at the end of the day. The wide aperture 50mm is a much cheaper option for APS sized sensors.

Portrait lenses have a few features…

1.long focal length. 35mm is too short. People start considering portrait lenses at 85mm (To start, you should use your kit lens at 55mm)
2.wide aperture. This controls the depth of field. You want a wider aperture to remove the distracting background. The background blurrs away. (To start, you should use your kit lens at f/5.6)

some very nice portrait lenses
85mm f/1.8
http://www.amazon.com/...B00005LE75

135mm f/2
http://www.amazon.com/...B00006I5J4

70-200mm f/2.8
http://www.amazon.com/...B00009MDBQ
(The gold standard of portrait lenses. People prefer this lens because it is so versisitile. The above are marginally better than the 70-200mm; but they are a bit more specializied.)