When you wonder about something, you want to learn more about it. You wonder why the car is making that noise so you ask the mechanic to explain it.
Wonder comes from the Old English word wundor, which means "marvelous thing, the object of astonishment." For example, the Taj Mahal is one of the great wonders of the world, so beautiful and magical. But wonders are all around us — anything that amazes and marvels is a wonder, like high-definition television, the Internet, your mom's homemade pizza — though we tend to forget this because we are used to them.