The Leader of the House of Lords takes charge of the government's business in the House, and has some responsibility for determining the order of speakers.
Unless (very rarely) the Leader is also a departmental minister, being Leader constitutes the bulk of his government responsibilities, but it has never been an independent salaried office. As an official position, the Leadership is of comparatively recent origin, although there has been a government minister in charge of the government's business in the Lords since at least the 18th century. Prime Ministers who sat in the Lords usually carried out its duties personally. The first female Leader of the Lords was Baroness Young in 1981-1983.
Leaders of the House of Lords