This is the Good Ideas window. Other programs call it "Tip of the Day", but I like "Good Ideas" better. It will appear whenever you start up Behold, until you uncheck the "Show this at startup" checkbox. There are a few useful tips for new users of Behold listed here. You can manually bring up this window with the Good Ideas command.
Show At Startup
Once you've seen these, you'll want to turn them off so they don't annoy you every time Behold starts up.