Every year on March 8th, countries around the world celebrate International Women’s Day. For many, it’s a day for action, a day to call attention to the injustices that women around the world still face. Phumzile Mlambo-Ngcuka is in that group—not surprising, given that she is the under-secretary-general of the United Nations and executive director of UN Women. Fortune took the opportunity to chat with Mlambo-Ngcuka about the significance of the day, the UN’s goals for women around the world, and what both businesses and individuals can do to make an impact.

The following interview has been edited and condensed for clarity.

Fortune: What is the purpose of International Women’s Day, in your view?

Mlambo-Ngcuka: It’s a celebration of the work that has been done by women. It’s celebrating activists, saying thank you to the women who continue to work. But it’s also an opportunity to reach out to new people, and tell them about what is going on and ask them to take action, whether it’s on equal pay or violence against women…It’s about calling everybody together to do something. It’s an opportunity for people to to learn more about what they can do.