Wide angle lenses get a lot into a picture, they make things in the foreground bigger than things in the background. Wide angle lenses, however this can cause distortion, particularly at the edges of the image. This can be exploited to create interesting images, but can be unflattering when used for portraits. It is however good for environmental portraits and establishing shots in a series of images. To reduce distortion, especially in ultra wide lenses, keep the camera flat and parallel to the subject, the more you tilt the camera the more noticable the distortion becomes.