What is a parliamentary select committee?

A select committee is composed of a number of MPs from across the parties in Parliament, represented in proportion to how many seats they have. They typically question witnesses (often properly grilling them!), produce reports for Parliament at large, and focus on specific areas or problems, such as the the Defence Committee, the Backbench Business Committee, or the European Scrutiny Committee. They can be drawn from either the House of Commons or the House of Lords, or both, as with 'Joint Committees'. Think of them as task forces, which specialise in their fields over time and help Parliament hold particular issues and actors to account more thoroughly than in open debate; and often in a constructively bipartisan (both party) fashion.