Scotland uses the British pound sterling (£), the same currency as the rest of the United Kingdom. The currency code is GBP.
Three Scottish banks—Bank of Scotland, Royal Bank of Scotland, and Clydesdale Bank—issue their own pound notes (£5, £10, £20, £50, £100). These are legal currency throughout the UK, though occasionally unfamiliar to merchants in England/Wales. They are backed 1:1 by Bank of England reserves.
Standard UK coins (1p, 2p, 5p, 10p, 20p, 50p, £1, £2) circulate everywhere.
Whether in Edinburgh, Glasgow, or the Highlands, the pound sterling is the only legal tender you need.