As a bill passes through Parliament, MPs and peers may suggest amendments - or changes - which they believe will improve the quality of the legislation.
Many hundreds of amendments are proposed by members to major bills as they pass through committee stage, report stage and third reading in both Houses of Parliament.
In the end only a handful of amendments will be incorporated into any bill.
The Speaker - or the chairman in the case of public bill committees - has the power to select which amendments should be debated.
In the Lords all amendments are debated. The Lord Speaker does not have the same power as the Speaker of the Commons.