There are two types of select committee – departmental and non-departmental.
The departmental select committees are charged with examining the spending, administration and policy of their specific department and its related public bodies. They may take evidence from witnesses and require the submission of documents within certain rules and they may set up sub-committees to carry out specific inquiries. They report to the House from time to time on topics of their choosing and, while the Government is required to respond within two months, but there is no requirement that reports are debated by MPs.
The non-departmental select committees, such as the Public Accounts Committee (known as PAC as well as the Select Committee on Public Accounts), the Public Administration Select Committee (known as PASC), the Committee on Standards and Privileges and the European Legislation Committee. They exist to consider issues within their specific, cross-departmental terms of reference.
The Committee of Selection nominates members for each committee after discussion by the Usual Channels. A motion is then put to the House, which normally approves the membership without debate or vote, although either may take place. New memberships are appointed after each election but these may be altered at any time. Normal membership is about 11 with party representation mirroring that of the House as a whole. Each committee elects a chair from its ranks, who normally serves for a whole Parliament.
The Liaison Committee is made up of all the chairs of the select committees. Its most prominent role is the questioning of the Prime Minister once every six months. The Modernisation Committee makes recommendations on changes to the House's practices. Its membership includes the Leader of the House.
There are other 'domestic' committees, which deal with the running of the House. These include the Accommodation and Works and Catering Committees.