There are two types of permission that may be needed when carrying out building work.
Planning
Planning seeks to guide the way our towns, cities and countryside develop. This includes the use of land and buildings, the appearance of buildings, landscaping considerations, highway access and the impact that the development will have on the general environment.
Building Control
Building Regulations set standards for the design and construction of buildings to ensure the safety and health for people in or about those buildings. They also include requirements to ensure that fuel and power is conserved and facilities are provided for people, including those with disabilities, to access and move around inside buildings.
For many types of building work, separate permission under both regimes (separate processes) will be required. For other building work, such as internal alterations, Buildings Regulations approval will probably be needed, but Planning Permission may not be.