This is the shorter and easier to remember alternative to the .co.uk domain extension and was introduced in June 2014. The .uk domain extension is used by companies and individuals to show they either do business or are located in the UK.
It brings the UK domain extensions in line with other european countries such as .fr for France, .es for Spain and .de for Germany.
There are no restrictions on the .uk domain extension meaning anyone can use and register a .uk domain extension. However if you own the .co.uk domain extension you are entitled to the .uk version for a period after they were introduced in 10th June 2014.