Corbetts are Scottish mountains over 2,500 feet (762 metres) and under 3,000 feet (914.4 metres), with a drop of a least 500 feet (152 metres) between each listed hill and any adjacent higher one.
There are 221 summits classified as Corbetts, and they are named after John Rooke Corbett, who originally listed them. Corbett joined the Scottish Mountaineering Club in 1923 and, in 1930, became the fourth person, and first Englishman, to complete the Munros.
Those who climb all 221 peaks are termed Corbetteers. John Rooke Corbett was the first person known to have climbed all the 2,500 foot peaks on his list. However in contrast to the numbers completing the Munros, the total number of people who have registered as completing the Corbetts is only in the hundreds. Completions are recorded with the Scottish Mountaineering Club.
Other hills within Scotland have been further classified as 224 Grahams (Scottish mountains over 2,000 feet/610 metres and under 2,500 feet/762 metres), 87 Donalds (hills over 2,000 feet/610 metres in the Scottish Lowlands) or 1,216 Scottish Marilyns (hills of any height with a drop of 500 feet/152 metres or more on all sides).
You can access an interactive guide to the Corbetts at the WalkHighland website.