To be au courant is to be well-informed about something. If you're au courant with local politics, you follow your city's elections and political controversies closely.
This word means being up to date on a certain subject. If you're au courant with a TV show, you've watched all the episodes, especially the most recent ones. Lawyers need to stay au courant on legal matters, and doctors need to be au courant on the latest medical research. In French, au courant literally means "with the current," or "in the course." If you stay with the flow of current events, culture, or work, you'll always be au courant.