How Many Countries Are There

It seems like a simple question. Just add them all up and you get the answer. The trouble is that different governments and organizations don't always agree on how many there are.
The reasons for the differences can all be attributed either firstly to politics, or secondly to the rather loose definition of a country.
The political problems come from some governments recognizing particular 'countries' whilst other governments claim that they are aren't countries at all.

For example, between the end of the Second World War and the fall of the USSR, the Soviet Union occupied Latvia, Estonia and Lithuania. As far as the USSR was concerned those countries were now part of the USSR and not independent countries. The UK, however, continued to recognize them as independent countries that had been 'occupied' by an invading force.

More recently Taiwan has been the main source of disagreement. Until 1971, it was a member of the UN and even the Security Council, but then China insisted that Taiwan was actually a province of China and not an independent country. The people of Taiwan, and its government, still insist they are not part of mainland China. Taiwan is recognized as being independent by some governments, but not all of them; it's not recognized by the United States.

China also considers Tibet to be another of its provinces - even though it had to invade it to take control - but most of the rest of the world has a very different view. So, if you are in China, there are already two 'countries' to remove from the list.

Definitions of what constitutes a country also vary. Some will go with the simple view that if it is a member of the United Nations (UN) it's a country. By that reckoning there are 192 countries in the world. But Vatican City is undoubtedly a country, and not a member of the UN, so that means the total must now be 193! Oh and then there are Taiwan and Tibet - so that's 195.

There are also very many colonies, territories and dependencies that are sometimes considered to be countries, and sometimes not. For example, Greenland seems like a country, but it is actually part of Denmark.

In the UK most of the population consider England and Scotland to be different countries, and Wales to be a principality. However, when it comes to international relations, they are all represented by the UK government, so according to many definitions they aren't countries or even nation states.

If you check the UK government web site they don't seem to view England and Scotland as different countries in an international sense. Instead they say of the UK:
The full title of this country is the United Kingdom of Great Britain and Northern Ireland. The UK is made up of England, Scotland, Wales and Northern Ireland. Great Britain (or just Britain) does not include Northern Ireland. The Channel Islands and the Isle of Man are not part of the UK.