To profess is to declare something, often insincerely. Your joy on the last day of school might lead you to profess that you'll truly miss seeing all the people who annoyed you all year.
You can profess something and mean it, but more often the verb profess is used when someone lies about their true feelings. You might profess your love of your grandmother's tuna casserole, or profess that you never bite your fingernails, but you're just saying what you think people want to hear. The original meaning of profess described taking religious vows, and came from the Latin word professus, having declared publicly.