The origins of the office are unclear, although it probably originated during Lord Burghley's tenure as Lord Treasurer in the 16th century.
The Treasury ministers together discharge all the former functions of the Lord Treasurer, which are nowadays nominally vested in the Lords Commissioners of the Treasury.
Of the Commissioners, only the Second Lord of the Treasury, who is also the Chancellor of the Exchequer, is a Treasury minister (the others are the Prime Minister and the government whips).
The Chancellor is the senior Treasury minister, followed by the Chief Secretary to the Treasury, who also attends Cabinet and has particular responsibilities for public expenditure.
The office can be seen as a sinecure, allowing the Chief Whip to draw a government salary, attend Cabinet, and use a Downing Street residence.