The Leader of the House of Commons is the member of the Government who is responsible for organising government business in the Commons. The Leader of the House attends the Cabinet and works closely with the Chief Whip. One of the Leader's duties is to tell the Commons about its business for the following week or two. This is done every Thursday. The Leader of the House of Commons post has historically been associated with the President of the (Privy) Council. This is not the case in the current Government formed in 2010. From 2010 the Leader of the House was, for the first time, not a member of the Cabinet but someone who attends Cabinet.
The Leader of the House of Lords is responsible for looking after the organisation of government business and procedure in the House of Lords. He or she is appointed by the Prime Minister and is a member of the Cabinet. Since the Lord Speaker has no powers to rule on matters of procedure, the Leader advises the House on matters of procedure and order. The Leader also expresses the feelings of the House on formal occasions, such as motions of thanks or congratulation. The Leader and his or her private office are also available to assist and advise all Lords, irrespective of party.
Office of the Leader of the House of Commons (external website)
Office of the Leader of the House of Lords (external website)