Certain types of development can be undertaken without needing to apply for planning permission. These are called ‘permitted development rights’.
An Article 4 direction is used to reduce the scope of permitted development rights either in relation to a particular area or site, or a particular type of development anywhere in the District. Where an article 4 direction is in effect, planning permission may be required for development that would otherwise have been permitted development. Article 4 directions are used to control works that could threaten the character of an area of acknowledged importance, such as conservation areas.
In Selby District there is one Article 4 direction (Millgate Housing Action Area) which removes some permitted development rights which means that you will have to submit a planning application for some work which would not normally require an application.
The Town and Country Planning (General Permitted Development) (England) Order 2015 http://www.legislation.gov.uk/uksi/2015/596/contents/made