Sanctions are way to financially isolate a target i.e. country or regime. They may be imposed for a variety of reasons i.e. political. military, social issues etc. Normally, they are imposed to change the behavior of a country or regime, incase where that country or regime is violating human rights, involved in terrorist activities or endangering international peace and security.
There are three types of Sanction
1) Comprehensive
2) Sectoral
3) Targeted
Sanctions can be imposed by the UN security council, the European Union and individual countries i.e. United States OFAC Sanctions