Overview
Ministerial Statements are either delivered in writing, or orally in person by the relevant Government Minister, appearing at the Dispatch Box in the House of Commons
Oral statements are normally delivered first to the Commons at about 12.30pm. After the Minister has read out his or her statement, opposition spokespersons then make a short speech in response, to which the Minister then responds. Brief questions from other MPs on all sides of the Chamber are then taken to which the Minister again responds.  The whole process normally takes less than an hour.
Government statements are repeated to the Lords by a relevant Minister at a convenient time after that. The Minister reads out the text of the statement made to the Commons.
Written Ministerial Statements were introduced so as to reduce the incidences of planted written questions being released. Written ministerial statements are released by Ministers, at relatively short notice, normally when they want to make an announcement to the House but feel that its content does not warrant a full Oral statement.
Urgent Questions
An Urgent Notice Question, is when an important matter arises, which an individual Member of Parliament believes requires an immediate answer from a government Minister (normally on that day).  These applications for an Urgent Question need to be filed by 11.30am on Monday, 10am on Tuesday and Wednesday, 8.15am on Thursday, and 8.30am on Friday. These applications are then reviewed by the Speaker of the House of Commons.
