Extradition is how someone who has committed a crime, or is suspected to have committed a crime, is handed from one jurisdiction to another. Usually, the country that wants the person makes a formal request to the other. Under international law, there is no obligation to extradite a person. There is a web of treaties, which state under what conditions extradition is possible.
In general: The offense for which the person is sought must be punishable in both countries, usually it must also carry a minimum sentence. The person extradited has the right to get a fair trial. The trial must not be political in nature. Many countries refuse extradition if there is the possibility of the death penalty being imposed, or of torture. Many countries refuse to extradite their own nationals
People who move to a different location to escape legal charges are called fugitives.
Examples
In 2019 protestors in Hong Kong demonstrated against a new extradition law proposed by the government of mainland China.