Former U.S. president Barack Obama just gave his biggest speech since leaving office—and he did it in South Africa to mark what would've been Nelson Mandela's 100th birthday at the annual Nelson Mandela Lecture.

In his lecture titled, "Renewing the Mandela Legacy and Promoting Active Citizenship in a Changing World," Obama appealed to people around the world to honor human rights and other values under threat, as well as to keep alive the ideas that Mandela worked for—democracy, diversity and for all to gain access to good education.

South African president Cyril Ramaphosa and Graca Machel, Mandela's widow, introduced Obama to a cricket stadium full of an estimated 14,000 people and even more who tuned into the lecture online.

Take a look at our five takeaways we learned during Obama's speech below.