When in doubt, refer to wikipedia :)
An extract for your information:
Official language : English
Regional languages :
1. "Scots" is the Germanic language variety spoken in Lowland Scotland and parts of Ulster (where the local dialect is known as Ulster Scots). It is sometimes called Lowland Scots to distinguish it from Scottish Gaelic, the Celtic language spoken in most of the western Highlands and in the Hebrides.
2. "Scottish Gaelic" [ˈkaːlikʲ] is a Celtic language native to Scotland. A member of the Goidelic branch of the Celtic languages, Scottish Gaelic, like Modern Irish and Manx, developed out of Middle Irish, and thus descends ultimately from Primitive Irish.