Imagine, you don't have a nationality. The day you die, there will be no more traces of you on earth. You can't get passports to travel and you're stuck in limbo. 99,99% of the people have a nationality but still a considerable amount doesn't have it. For example in Myanmar there are 803,075 Rohingya people without citizenship because they are not recognized in their country. In Syria there are 231,000 Kurds that are stateless. And in Brunei it's impossible for foreign cheap labor force to get the nationality even if they all ready live for generations in Brunei and because of this lost their nationality in their home countries.
The UN has a definition for the stateless: A person who is not recognized by law as a citizen of a country. For example a girl lives in Japan with her Japanese boyfriend. She wants to merry him and become Japanese. When she unregistered her nationality in her home country a few day later her Japanese boy friend gets run over by a car and dies. Result she is stateless because she didn't have time to merry her Japanese boyfriend and already lost the nationality of her home country.
In a world where borders are not so important anymore the idea of multiple nationalities is starting to exist again. How can you get the nationality by having a bond with a country, by marriage, by your family tree, by were you were born, where you lived for a long time. But sometimes people lose their nationality. This is why UNHCR asks to make statelessness impossible by law. But the question of nationality is a sensitive issue in Politics.
The Americas is a place where statelessness hardly exists because every child that is born on US or Latin American soil is granted the nationality. With the destruction of the USSR, a lot of people became stateless because the administration was so busy with the economical crisis its lost track of a good nationality distribution system between all the countries. So a lot of people didn't get regularized. Now there are almost 20.000 stateless people in Ukraine and For Germany there are 10.000 people almost who became stateless after the unification of East and West.
So which are the most important reasons to be stateless? First because of the falling apart of states for example the recent case of Sudan and South Sudan. Also because of discrimination of for example the Roringya people in Myanmar. Because of conflicts and holes in the law of a country.
UNHCR is giving global attention to Statelessness, High Commissioner Gutierrez told that there was a real breakthrough in the last years. UNHCR pleads that states guarantee nationalities waiting for Sustainable status.