Short answers, pulled from the story.
The Scottish Lowlands is a cultural and historical region of Scotland lying south and east of a line between Stonehaven and Helensburgh on the Firth of Clyde. It includes cities like Edinburgh and Glasgow and covers the Central Belt as well as the Southern Uplands near the Anglo-Scottish border. Despite the name, some parts of the Lowlands reach elevations of up to 2,766 feet.
Approximately 80 percent of Scotland's population lives in the Central Belt, also known as the Midland Valley, which is the core of the Scottish Lowlands. That figure represents around 3.5 million people concentrated in the river basins of the Forth and the Clyde.
The Lowlands and Highlands diverged culturally from the Late Middle Ages into the modern period, primarily through language. Lowland Scots replaced Scottish Gaelic throughout most of the Lowlands, with Gaelic retreating from most of the region by the 15th century and persisting in Galloway until the 18th century. The Gaelic-speaking Highlands named the Lowlands a' Ghalldachd, meaning the foreigner's land.
Using the Boundary Fault as the dividing line, sixteen traditional Scottish counties fall entirely within the Lowlands: Ayrshire, Berwickshire, Clackmannanshire, Dumfriesshire, East Lothian, Fife, Kinross-shire, Kirkcudbrightshire, Lanarkshire, Midlothian, Peeblesshire, Renfrewshire, Roxburghshire, Selkirkshire, West Lothian, and Wigtownshire. Five counties including Angus and Perthshire straddle the fault.
Many ancestors of the Scotch-Irish in the United States, also known as Ulster-Scots, originated from the Scottish Lowlands and Borders region. In the 17th century they migrated to the Ulster Plantation in Ireland, and many then moved again to the American frontier, a large portion arriving before the American Revolution.
Military units associated with the Scottish Lowlands include the Lowland Brigade, the Royal Scots, and the 52nd (Lowland) Infantry Division. These regiments drew recruits from across the Central Belt and surrounding Lowland counties.