Edge-lit
Edge-lit literally means „lit from the edge": the LEDs sit in the frame and shine into the surface from the side instead of behind the artwork. You will often see the term on manufacturer pages and in the data sheets of LED light frames.
Its counterpart is backlit, a full backlighting solution where the LEDs are distributed behind the entire image area. Edge-lit is flatter and lighter; backlit allows more light output on very large or especially bright surfaces.
How edge lighting works technically, and why it needs special lenses and a certain frame depth, is explained in our entry on edge lighting.