A bill is a proposal for a new piece of legislation that - if approved by a majority in both houses - will become an act of Parliament and law of the land.
Stages a bill must pass in both the Commons and Lords
The title of a bill is read out and copies of it are printed but no debate takes place.
A review of a bill that has been amended at committee stage.
The House takes an overview of the bill as finally amended - before passing it on.
Most important bills are introduced by a government minister and relate to public policy - this is why they are called public bills.
Such bills are usually introduced in the Commons, where they must pass a series of stages known as readings before peers undertake a similar process in the House of Lords.
Some bills, usually of an uncontroversial nature, are introduced in the Lords - facing scrutiny by peers before being passed on to MPs.
During this passage through Parliament, bills may be altered by MPs or peers - acting on behalf of the government or from the backbenches - either by adding new clauses or by amending existing clauses in the draft bill.
An MP or peer hoping to make such an alterations will need the support of the majority of his or her colleagues if it is to prove successful, as they are often pushed to a vote.
In the event of a disagreement between the Commons and the Lords, a bout of parliamentary ping-pong may ensue - where legislation bounces back and forth between the Commons and the Lords as each House reviews the amendments made by their counterparts until differences of opinion are resolved.
But if no such resolution is reached, the government may invoke the rarely-used Parliament Act - a piece of legislation which means that MPs can over-ride the will of the House of Lords.
The bill becomes an act when it has completed its passage through Parliament and receives Royal Assent - the approval of the Monarch.
Royal Assent has never been withheld in recent times.
Private members' bills
These are normally introduced by backbench MPs and peers to raise awareness of a particular issue as they often stand little chance of becoming law without government support.
However, some private members' bills do make it through Parliament and onto the statute book, such as David Steel's 1967 Abortion Act or Sydney Silverman's 1965 act on the abolition of hanging.
Private members' bills are a type of public bill and should not be confused with private bills.
Rarely introduced, private bills normally affect specific private interests and are often introduced by MPs on behalf of companies.
They are used, for example, to facilitate plans to build a railway line, rather than for matters of public policy.