What is the standard of the British standard socket hole?

British standard socket: one vertical on the top, two horizontal on the bottom, voltage 230V, frequency 50Hz.

British standard socket:

British standard plug:

British standard plug is available in Hong Kong and the United Kingdom, India, Pakistan, Singapore, Malaysia, Vietnam, Indonesia, and the Maldives Used in countries and regions such as Qatar and Qatar, it is characterized by three square heads.