NGOs are non-profit organizations that work on issues like human rights, the environment, health, poverty eradication, and rehabilitation. They are legally registered private organizations that do not work for profit. NGOs aim to bring positive change to society and depend on funding for their operations. They play important roles like experimenting freely, adapting to local needs, building rapport with local communities, and recruiting motivated staff. However, NGOs also face challenges like lack of funds, leadership, trained personnel, and ensuring coordination and public participation.