With a travel warning, a state wants to protect its citizens and ensure that they do not travel to dangerous areas in other states. An area can be dangerous because war is being waged there. Or it may be dangerous to enter an area because of a natural disaster or an epidemic.
A travel warning is also issued if a war or disaster is likely but has not yet happened. This applies to poor countries, for example. In many countries, democracy does not work, or groups want a different government by force. The political situation is then unstable, they say. Instead of war, these groups often try to cause terror with terrorist attacks.
Especially tourists from rich countries can be kidnapped. They are taken to an unknown place. In order for the abductees not to be killed but released, the armed groups demand a high ransom. That would be extortion. There could also be robberies of hotels and cars, rapes or other crimes. Tourism is an important part of the economy in many countries. If tourists are threatened, a country will eventually lack money, which in turn would be good for improving the insecure situation.
Travel warnings are constantly kept up to date. You can find out about a destination on the internet and check the website of the Ministry of Foreign Affairs to see whether it is currently dangerous in the whole country or in individual areas. If this is the case, it is better not to travel. Travel companies can often rebook you on another flight free of charge or refund your money for the holiday. In any case, it is cheaper than having to deal with an insurance company because of damage or problems abroad.