Ham Radio, or Amateur Radio, is a world wide radio service devoted to experimentation, public service, and promoting international good will. There are hams in almost every country of the world that share in this hobby. There are many areas of interest in Ham Radio, way to many to generate a complete list here. But the span of interests range from talking to friends down the block to making new friends around the world, bouncing signals off the moon, building, launching, and using dedicated amateur satellites. Types of communications from Morse code to voice to digital data to television. Communicating strictly for personal interest, handling messages for others for public service or emergencies, or participating in world wide radio contests.
In past years the image of a Ham Radio operator was that of an electrical engineer or technician that had a maze of wires and home built equipment in his basement. Over the years this has changed and now the people in Ham Radio range from truck drivers to kings, housewives to househusbands, kids to retirees. There are also Hams with disablities of many kinds. Today you can buy radios and other station equipment off the shelf from international manufacturers, or if you want to you can design and build your own. You can get radios that fit in your shirt pocket, fit in just about any car, hide in a cubby hole of a writing desk, or fill a room with equipment.
And it doesn't have to be expensive. Used equipment can be purchased at flea markets or from dealers for very reasonable prices. You can easily get on the air for around $100 or even less with a little looking around. Some clubs even have loaner gear for those just getting started to use until they get their own. And some clubs have stations that can be used by members and guests.
Around the world there are various agreements between countries that in many cases can allow you to use your existing license as you travel. There is more of a movement to create an international license that can be used in more countries as travel becomes easier. Ham radio is a great way to find out about the spots to visit when you travel that most tourists don't see, and you may find yourself invited to visit with Hams where ever you go.
Feel free to look around my site, I have a small sampling of links to other sites about Ham radio and related topics. Those will lead you to more, and more, and more. Ham Radio has a large variety of information available on the WWW and other Internet services.
More information about Amateur Radio is available from the ARRL Ham Radio info page.