Non-governmental Organizations are groups that are not official parts of any state government. They are, instead, created and run by private individuals or groups. NGOs are typically involved in trying to solve one particular problem or type of problem.
Some major NGOs include Doctors Without Borders, the Red Cross, and the Bill and Melinda Gates Foundations. These NGOs work in many countries of the world to try to improve the lives of the people. For example, Doctors Without Borders and the Red Cross have done work in disaster areas such as Haiti which do not have enough medical infrastructure to cope. The Gates Foundation has worked on improving public health and education around the world.
For international relations theorists, NGOs are important because they can help solve world problems and can increase the amount of contact between different nations. Both of these will reduce (theorists believe) the amount of conflict in the world.