What is social work, what makes it distinctive, and where do its boundaries lie? ‘What is social work’ provides a short definition: it is a community-based response to social need. Social workers spend their time trying to ease social suffering. They encounter the extreme casualties of social inequality—the victims of poverty, illness, addiction, and abuse—and they operate in the space between the state and the poor or marginalized. A broad definition is necessary when looking at any social phenomenon internationally, because of political and cultural variations. Important themes in social work’s history are also considered along with the boundaries with other professions such as public health, counselling, psychotherapy, and community development.