Ham radio is licensed by the country you live in. In the US, the basic technician license is very cheap and the test to get it is fairly easy with an abundance of online materials, including answer keys, to study. The reason these licenses are important is because ham operators need to operate within legally defined band plans, or radio frequency allocation guidelines. Emergency services, search and rescue, your nations military, all use specific radio bands given to them by the government. The license helps teach you how to avoid interfering with someone who can get you into serious trouble. It also helps keep you safe, and requires you to learn some basic electrical knowledge that frankly will be mildly useful the rest of your life. Amateur radio is a really fun skill that isn’t that hard to learn. If you have any more questions, feel free to ask and if you want specific information about your countries licensing, Im happy to help look it up.

EDIT: Just to add, you can always listen without a license. That’s why scanners exist, but you need a license once you hit the button to transmit on a ham radio frequency.