Legislation goes through a number of stages before it becomes law. These are the same in both Houses. Bills (other than Money Bills) can start in either the House of Commons or the House of Lords. They go through the following stages in each House, though with important procedural differences in both Houses: first reading, second reading, committee stage, report stage and third reading. Once the Bill has completed these stages in one of the Houses, the process is repeated in the other. After this any amendments from the second House are considered by the first. When both Houses agree on a Bill then it may be presented to the Queen for Royal Assent.
Further information on this subject can be found from the following links.
About Parliament: Bill stages
About Parliament: Passage of a Bill
Related glossary term: Bills
Related glossary term: Acts of Parliament
Related glossary term: Royal Assent