It's exactly like teleporting. [Don't mind him, he's already heading off in that direction and making a beeline for that box.] It's...well, it's quite difficult. You can't even Apparate without a license, and you can't have a license until you've passed the test, and you can't even take the test until you're seventeen. It takes a lot of concentration because with Apparition, you must clearly focus on where you want to go. If you don't focus, you risk a lot of injury. Splinching, you know.