Board selection at buildin and why exist skyrim overlay

[Yebjhar Se væran]

Hello, I'm building chromium os and I'm selecting the board, so while searching in overlays i got some pretty interesting things, but as I don't know to what overlays are used in general and yhe greate variety of them, which one can i use, also an extra quaestion, why there is a overlay called skyrim? like the videogame