Separation and Rim lighting examples - Studio

Separation Lighting 

Accent and/or separation lights become more important with corrective lighting. Because we use darkness/shadow to our clients' benefit, we must use small, controllable light sources to highlight only the areas we want the viewer to see. We often light a three-quarter or full-length portrait as a head-and-shoulders portrait (with our main light and reflector for fill), then use accent/separation lights to selectively illuminate the rest of the body. This gives us, as photographers, complete control over the outcome of the final image—and gives our clients a final portrait their egos can handle.
(source:http://www.sekonic.com/whatisyourspecialty/photographer/articles/the-separation-light.aspx)

Separation and rim lighting

Rim lighting
Rim lighting is the same as backlighting, where the subject is lighted from behind causing the facial features of the profile to be highlighted.  
(source: http://en.mimi.hu/photography/rim_lighting.html)