1. Could inform someone of the facts or several pieces of information (about someone or something). I know you're from the countryside and not used to city folk, but I could teach you a thing or two about New Yorkers. If you want to learn about the history of cinema, then you should ask Jeff—he could teach you a thing or two.

2. Could correct or confront someone about his, her, or their mistaken belief or incorrect point of view (about someone or something). That jerk has been making snide remarks all night. I could go over there and teach him a thing or two about how to talk to women!