You'll find the United Kingdom off the northwest coast of the European mainland, across the English Channel from France and across the North Sea from Norway. The UK actually comprises a group of islands. The main island, Great Britain, is made up of the countries England, Scotland and Wales. Northern Ireland is part of the UK too, but that forms the northern tip of the island of Ireland to the west. If you have a rental car you'll find the UK is highly populated and developed with major cities, including the capital London, and Glasgow, Manchester, Birmingham, Edinburgh and Cardiff. But there are plenty of sparsely inhabited areas too, like the mountainous 'Highlands' of Scotland and large areas of mid-Wales.
Renting a car is one of the best ways to explore the UK's huge variety of sights. The distances aren't great and the road connections are generally good. You can drive from the world famous attractions of London in the southeast to the beautiful wilderness of the Scottish west coast in a day. So it's easy to see city sights like Big Ben, Windsor Castle and Buckingham Palace, and then spend time at the acclaimed beaches of Cornwall or cross the sea to visit the Giant's Causeway in Northern Ireland. There are attractions in every part of the UK, whether it's culture, nightlife and style in the cities or the natural wonders, beachlife and history of the quieter regions.
You'll find that driving in the UK is generally easy and safe. There is a good network of motorways and well-signed trunk roads. The major problem could be traffic. Try to avoid peak rush hours and the beginning and end of major holiday weekends. Even motorways can become jammed. The driving basics are: drive on the left, don't exceed 70 mph and look out for changeable speed limits. These new 'smart' signs can change with the weather and traffic conditions. Note that you must stop when traffic lights are red and must normally drive on the left-hand lane on multi-carriageway roads.