The Schengen Agreement is an agreement that was signed among European countries in 1985. This agreement aims to abolish border controls among its members and allow for the free movement of people and goods within the Schengen Area. Currently, there are 26 European countries that are part of the Schengen Area, which includes most EU member states, as well as four non-EU member states: Iceland, Norway, Switzerland, and Liechtenstein. However, the United Kingdom is not a member of the Schengen Area.

The UK has been a member of the European Union since 1973, but it has chosen to opt-out of the Schengen Agreement. This means that the UK still maintains border controls, passport checks, and visa requirements for people entering and leaving the country. The UK`s decision to opt-out of the Schengen Agreement has been a topic of discussion in recent years, especially since the Brexit referendum in 2016.

Brexit has caused a significant impact on the UK`s relationship with the EU, including the Schengen Agreement. Following the UK`s departure from the EU, the UK`s status as a non-Schengen country will remain unchanged. This means that UK citizens will continue to face border checks when entering Schengen Area countries, and non-UK citizens will still face border checks when entering the UK.

One of the main reasons why the UK has opted-out of the Schengen Agreement is due to concerns about national security. The UK has a robust border control system in place that allows authorities to keep track of who is entering and leaving the country. This system has been effective in preventing terrorist attacks and other criminal activities, making it an essential part of the UK`s national security strategy.

In conclusion, the UK is not a member of the Schengen Agreement, and its decision to opt-out has been a topic of discussion in recent years, especially after Brexit. The UK has chosen to maintain its border control system to ensure national security, which means that UK citizens will continue to face border checks when entering Schengen Area countries, and non-UK citizens will still face border checks when entering the UK.