Letterbox format
From LGPedia
Conventional television uses a 4:3 width to height ratio, while HDTV uses a 16:9 "wide screen" width to height ratio. Over time movies have used a variety of format but these are almost all variants of a "wide screen" format. When wide screen content is coverted for use on a convention 4:3 screen a section of the screen has to be selected for use or what is more commonly done is the content is converted to a Letterbox format with a black area at the top and bottom of the screen to compensate for the different ratio. Both YouTube and Revver use the conventional 4:3 ratio.
In the LG15 series, Bree's videos tend to use the conventional 4:3 ratio while many of Daniel's videos have been formatted with the letterbox style.