Edge Detect has only one control: Angle. This determines the angle of your edges. Edge Detect will remove all the color from your image except for the color within the edges:

Emboss also has Angle as its only control. It turns your photo into a gray-scale image but makes all the lines look raised or embossed.

Outline takes all the edges of your image and turns them black against a white background. It has two controls: Thickness, which controls how thick the black outlines will be, and Intensity, which determines how intense the edges of the black line will be.

Relief leaves the color of your image intact but "raises" the image lines just like Emboss. This will give your image a little texture, but it can also make your image look a little bit like you have slight double vision:

Relief also has Angle as its only control.