The backstop is part of the draft withdrawal agreement negotiated between Theresa May`s government and the EU. Following the DUP`s objections, Mrs May agreed on a backstop in which the whole of the UK would indefinitely maintain a very close relationship with the EU, namely the maintenance of the customs union. Both the UK and the EU agreed that opening the border and respecting the terms of the Good Friday agreement were essential in negotiations on a post-Brexit deal. That is why they have committed themselves to the principle that, even if future trade negotiations fail, there should be provisions to ensure that the border remains as open as it is today. This principle is the Irish backstop. In July 2019, Theresa May resigned and Boris Johnson became Prime Minister, with Boris Johnson saying he wanted to replace the Irish backstop as part of the withdrawal deal.  On 19 August, in a letter to the President of the European Council, the Prime Minister declared that the agreement was “undemocratic and incompatible with the sovereignty of the United Kingdom”.  He stressed that this was “not compatible with the UK`s desired end goal” for its relations with the EU. Its third reason for the unsurability of the backstop is that it “weakens” the Good Friday Agreement and the peace process in Northern Ireland. Tusk said opponents of the deal, without “realistic alternatives,” supported the re-establishment of a hard border on the island of Ireland. That`s the reality, “even if they don`t admit it,” he added. “The backstop is an insurance to avoid a hard border on the island of Ireland, unless an alternative is found,” Tusk tweeted.  The Irish Government considered that “the real objective of the backstop was to maintain the status quo by guaranteeing freedom of movement and not a hard border on the island of Ireland; which is of paramount importance to the GFA.
The reality is that Brexit is a threat to the GFA.  What is the backstop? The backstop is essentially an insurance policy or a safety net that would prevent the reintroduction of a hard border with customs controls on the island of Ireland after Brexit. The “Irish Backstop” is practically an insurance policy in the Brexit negotiations between Britain and the EU. It aims to keep the Irish border open (as it is today), regardless of the outcome of negotiations between the UK and the EU on their future post-Brexit relations. The Irish government supported this proposal.  It was strongly rejected by the Democratic Unionist Party as a weakening of Northern Ireland`s place in the UK and is seen as the main reason why Theresa May`s withdrawal agreement was never approved by the British Parliament.  The British government had rejected the original proposal. Prime Minister Johnson called the backstop “undemocratic” and called for its removal from the divorce agreement.