The act of accepting something as the truth is believing. For many kids, believing in the Tooth Fairy is an important part of childhood — not to mention an excellent source of cash!
Have you ever heard the phrase "seeing is believing"? This basically means that if you witness something in person, you're more likely to accept the fact that it's real or true. To believe is to trust in this truth. And for many people, believing isn't about having proof — it's about accepting something as true even without seeing it. Most religions, for example, emphasize the importance of believing in a higher power.