What is a hard border?

In the context of Brexit, a ‘hard border’ refers to any physical infrastructure, from remote cameras to guard posts, that might be put in place along the border between Northern Ireland and the Republic of Ireland to monitor and process the movement of people and goods. After the end of the transition period, the UK will leave the EU’s single market and customs union, meaning customs checks will be needed between the UK and the EU, including Ireland. In order to avoid the need for such infrastructure on the UK’s land border with Ireland, the UK and the EU agreed in the Withdrawal Agreement that there would be customs checks on goods moving between Great Britain and Northern Ireland to avoid such checks on the island of Ireland itself and prevent the need for a hard border.