“Etre au courant de” is our way to say “to be aware of” or “to know about”.
On va à Montréal cet été. Oui, je suis au courant. – We are going to Montreal this summer. Yes, I know.
Je suis au courant de tes problèmes. – I am aware of your problems.
Another common expression using the word “courant” is “tenir au courant.” It means “to keep posted.” It’s a casual expression often used at the end of an email.
Tiens-moi au courant! – Keep me posted!
Tu viens au concert avec moi? Je te tiens au courant – Are you coming to the concert with me? I’ll keep you posted.