What the Lords does
The House of Lords is the upper chamber of the UK Parliament. It scrutinises and amends legislation passed by the House of Commons, provides a check on executive power, and produces detailed reports through its committee system that often inform policy. It can delay legislation and send it back to the Commons with amendments — a process that can be repeated (ping-pong) until agreement is reached.
What the Lords cannot do
The Lords cannot permanently block legislation that the Commons supports. Under the Parliament Acts 1911 and 1949, the Commons can ultimately bypass the Lords entirely for most legislation if the Lords refuses to pass it in successive sessions. The Salisbury-Addison convention holds that the Lords should not block legislation that was in the governing party's election manifesto.
Who is in the Lords
The Lords has three main categories of peer. Life peers (the majority, around 650): appointed by the monarch on the Prime Minister's recommendation, they hold their peerage for life but it does not pass to their children. Bishops: the 26 Lords Spiritual — the Archbishop of Canterbury, the Archbishops of York and 24 other Church of England bishops — sit by virtue of their office. Hereditary peers: as a result of the 1999 House of Lords Act, only 92 elected hereditary peers remain (pending further reform).
The reform question
Lords reform has been debated for over a century. The 1999 reforms removed most hereditary peers, leaving a predominantly appointed chamber. Proposals for a fully or mainly elected upper chamber have been made repeatedly but have not been implemented, partly because of disagreement on the model and partly because reform requires the Commons to agree to create a chamber that might more legitimately challenge it.