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Members of the House of Lords are not publicly elected. Historically the Lords were hereditary peers entitled to sit in the chamber because they held an inherited title such as duke, marquess, earl, viscount or baron. These days most of the Lords are appointed by giving them the title of life peer - they make up 707 out of 824 members (excluding some through long-term sickness, etc.). Life peers do not pass their title on to their children. Plans for further reform of the Lords are being considered. The main purpose of the Lords is to scrutinise proposed new laws to make sure they are fair and workable. Some government bills will be sent to the Lords for their first reading to spread the workload between the two houses.
The House of Commons is the most powerful of the two houses of parliament. It is made up of 650 MPs, almost all members of political parties and each representing different constituencies or areas of the country.
Policies and laws are debated here - although some powers have been devolved to Scotland, Wales and Northern Ireland, and some laws are made in Europe.
The party which wins more than half the seats in the Commons wins the election and forms the government. The new prime minister makes about 100 MPs ministers. These ministers form the government and take the lead in representing key departments like justice and education. In the May 2010 election, no one party had an absolute majority so the Conservatives and Liberal Democrats joined forces to create a coalition government. Liberal Democrats currently make up about a fifth of the coalition government.
The cabinet is the central decision-making group of parliament made up of about 20 ministers chosen by the prime minister. As the government is currently a coalition the deputy prime minister also has a say about who is in the cabinet.
The first cabinet after the May 2010 election included 23 ministers - 18 Conservative and five Liberal Democrats.
Cabinet members have a collective responsibility, which means they all have to support any decisions which are taken.
The opposition is usually the second-biggest party in parliament - since the May 2010 election, this has been Labour.
Twenty days in each parliamentary session are set aside for opposition day debates - 17 for the largest opposition party and three for the smaller parties. The opposition generally uses them to raise questions of policy and administration. The opposition leader challenges the prime minister during Prime Minister's Questions when he can ask six questions.
Since the May 2010 election there are nine smaller parties represented by MPs in the house, apart from the three main political parties. These include the Scottish National party and Plaid Cymru, as well as one Green party MP, one Respect MP and one independent.
The Liberal Democrats are part of the coalition, so they sit on the government benches in the Commons. Nick Clegg, the leader of the Lib Dems was made deputy prime minister after the May 2010 election and five more Lib Dems were included in the first cabinet. Lib Dem ministers in the coalition are bound by collective responsibility so they have to support cabinet decisions on key issues like the economy and foreign policy. But it has been agreed that Lib Dem MPs will be permitted to abstain in a vote in the Commons on certain issues where they disagree with the Tories.
Backbenchers are MPs who don't hold ministerial or shadow cabinet posts. Lacking responsiblities to a department they aren't as bound to the government, or front bench, and can speak more freely and even vote against the government if they wish.
They can sometimes introduce their own ideas for legislation in the form of a private member's bill. Backbenchers are so-called because they sit on the back row of benches.
The prime minister is usually the leader of the party with a majority of seats - i.e. more than half the MPs in parliament. The prime minister is responsible for choosing the cabinet and also has meetings with the Queen.
He has to answer Prime Minister's Questions in the Commons every Wednesday. Questions can come from any MP on any subject.
In the May 2010 election the Conservatives were short of an absolute majority. David Cameron became prime minister after forming a coalition with the Liberal Democrats.
Since the coalition was formed, Liberal Democrat leader Nick Clegg has been the deputy prime minister. Deputy PM questions are held about every five weeks.
These 30-minute sessions cover the policy aspects the deputy PM is responsible for, which include political and constitutional reform.
He is also lord president of the privy council. As deputy PM, he is consulted in any decision involving the prime minister
The speaker is the chief officer of the Commons and is elected by MPs.
He takes charge of debates in the Commons, choosing which MPs should speak and calling MPs to "order" when debates become unruly.
Although he or she is usually a member of one of the main parties, once elected the speaker puts party politics aside and has to act impartially.
The person in charge of the opposition party becomes the leader of the opposition.
Gordon Brown stood down as Labour party leader after losing the election in May 2010 and Ed Miliband won the subsequent contest for the leadership.
There's also an opposition leader in the Lords. The opposition leader in the Commons picks members of the shadow cabinet.
Each member of the shadow cabinet scrutinises a different government minister's department and devises policies in that departmental area.
One of an MP's most important roles is to help make and change the laws governing the UK. Both houses of parliament generally have to agree on a new law - after a process which can take months, or even years. Click through the slideshow to find out about the key stages in the passage of a bill.
Continue reading the main storyHow new laws are made
- After a new government is elected, the Queen makes a speech to Parliament which includes a list of bills or proposals for new laws. Some of these bills may have already been through one or two kinds of consultation: green papers contain ideas for bills, white papers include more definite proposals.
- Most bills start in the Commons. The first reading is a formality. At the second reading MPs debate the main principles. In 2005 Labour had plans to extend maternity leave. The Work and Families bill had broad support at second reading so the bill moved to committee stage without the need for a vote.
- MPs can introduce their own legislation in the form of a private members' bill. In 2009 Labour MP Julie Morgan wanted a ban on under-18s from using sunbeds. She won government backing and her bill moved to the committee stage - without government support a bill is not likely to progress any further.
- All the bills that pass the second reading are considered by a public bill committee of at least 16 MPs. They consider a bill line by line and may introduce amendments. They can call experts to give evidence and they may meet several times before returning the bill to the Commons.
- At the report stage further changes can be made. At this point there could be a rebellion and parts of the bill might be defeated in a vote when MPs divide into two areas known as the Aye and No lobbies. The bill then moves to a third reading when there is often a brief debate before it goes to the Lords.
- A bill goes through the same process in the Lords. This time, all members can take part at committee stage. Most bills need the Lords' approval but occasionally the Commons will use the Parliament Act to pass a bill into law. This happened in 2004 when the act was used to force through a hunting ban.
- Any Lords' amendments are returned to the Commons for consideration. A bill can go backwards and forwards several times before both houses agree on a final version and it gets the royal assent. Labour's bill on maternity leave was unopposed so it became an act that came into force in April 2007.
Plans of the House of Commons and House of Lords based on information from www.parliament.uk
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