Speedlight for Nikon?

Hi, I'm looking for a Speedlight for my Nikon camera since I do portrait photography, but I can't afford the really expensive SB-800s and so on, so I looked around and found the Yongnuo YN-565EX. However, it said "for Nikon SB-800, SB-900, etc". Does this mean it has to be the slave for an SB-800 or such? Or can I use it on the camera on its own.

For YN-565EX it can be triggered as a slave from OEM Canon or Nikon triggers. It can also be on the camera on its own.

If you are doing portrait photography, then ideally you shouldn't have the speedlight on camera - you'll just have on axis (flat) light, unless you plan to boune the light off a nearby (neutral coloured) surface.

You can't control the direction of light sufficiently for portrait work if the light is on camera. I recommend you look at getting off camera manual flashes like the YN560, rather than the TTL version you are looking at, and learn to light manually.

A YN560 costs around £30 and a set of radio triggers costs around £20. You would need to be able to shoot in manual exposure mode on your camera.