I think you did a lousy job of explaining what an open interest means.
If I were you, I would explain that open interest is comparable to common stock float . While common stocks has fixed authorized number of shares that cannot be changed unless authorized to split or reverse.. Stock options has nothing to start with but open interest that grows or shrink depending on the outstanding number of options that are bought to open and sold to close or whatever like straddles, and those crazy option strategies used by traders. Why open interest is important to know is to give a trader an idea of the popularity of that specific option in specific price and date of exercise. Volume is the same definition between common stocks and options except that options is every hundred shares per volume. I often find it begging to improve explanations of stock options , people sems to be so glib about explaining it to readers as if they float over their heads with assumptions that they understand what they are saying or hearing.