The lights are on but nobody's home ... me thinks. 

I've always referred to "margin lights" as "flankers"  ..... they are a vertical row of glass to let addition light in....can flank window and doors... often found on the second two story front wall of a home that would normally have palladian window.... to get the same effect but for less money, builders often install a double hung window with two flankes and a half round or elliptical window or solid piece on top....

more than anyone needed to know, I'm sure!!

I am glad to see that my adviser, Barbara Todaro, has provided an answer. 

Those windows at the side of an entrance door to see if someone is coming to answer the doorbell!

That time between night and day when the light is marginal.

Side light the side of the door so people can look in when you're trying not to answer the door.

Tony and Suzanne Marriott, Associate Brokers I have these on my front door and didn's know what they were called. Barbara Todaro and Raymond E. Camp straightened out.

I have no idea. 

Barbara Todaro has the correct answer but I thoroughly enjoyed the response by Kathleen Daniels.

Barbara seems to have this one nailed.

They are used in doors and I remember them near doorways in older school buildings to be able t see what was going on.

Around the edges.

A light fixture taht should have been bigger.

Barbara Todaro has the definitive answer!

Promise!!!

Barbara Todaro's answer!

Looks like Barbara gave you a great answer.

Designer Lighting that can be hung above vanity, hung above a dining area, or along kitchen ceiling, or ...surrounding entertainment center,or lights margining along windows or even pathways, and hallways..use your imagination for Margin Lighting.