Parliament is a national legislature that carries out the legislative function of government. It can be unicameral (one chamber) or bicameral and it can be directly elected or appointed. The executive function is largely carried out by the prime minister and his or her ministry. The judiciary is independent of the executive.
A defining feature of the Westminster system is that bills must pass through several distinct stages, called readings, in each house before they can be voted on as law. First reading is merely a formality; second and third reading involve more detailed consideration of clauses of the bill. In addition, most parliamentary systems require a bill to be passed through two sets of readings before Royal Assent can be granted.
In parliamentary systems where MPs are democratically elected it is important that citizens have a sense that their representatives represent them. This is why many parliaments have outreach offices that facilitate interaction between MPs and citizens. More affluent parliaments may also provide MPs with elaborate telecommunications systems and devices to enable them to communicate more effectively with their constituents.
The way in which a parliament conducts its business varies significantly from country to country. However, most parliamentary systems are based on a common set of conventions that include a semi-circle layout, elected chairs and members of select committees and a requirement that any motion for backbench business must be agreed by the Whips before being debated. The office of the Parliamentarian compiles a series of procedural decisions for scholarly publication, called precedents, and publishes House Practice, a condensed compilation of procedures of current application.