From Wikipedia: "Amateur radio is a hobby and, by law, completely non-commercial. Individual amateur "ham" radio operators pursue the avocation for personal pleasure through building their own radio stations and communicating with their fellows globally, and for self-improvement via study and practice of electronics, computers, and radio and TV wave behavior. Radio amateurs are, thus, "amateurs" in the true sense of the word: pursuit of an activity only for the love of it. Radio amateurs can not broadcast or transmit music and other general public entertainment programming. The amateur radio use of the air waves is for personal satisfaction and for forwarding the "state of the art" of electronics and communication techniques. Amateur radio operations can be detected in designated bands throughout the radio spectrum, using a variety of modulation methods including Morse code, voice and digital modes, and image modes such as television and facsimile."
Despite what it may suggest, amateur radio users are not inexperienced, or untechnical. It simply means that they are not allowed to earn money from their hobby. In fact, they have contributed greatly. As Wikipedia says, "Throughout the history of amateur radio, amateur radio enthusiasts have made significant contributions to science, engineering, industry, and social services. Research by amateur radio operators has founded new industries, built economies, empowered nations, and saved lives in times of emergency."
The Internet is amazingly useful, and has changed our lives immensely. It provides almost global, almost totally reliable communication. VOIP software like Skype makes keeping in touch with people in other countries simple. However, it relies on mains electricity, and cables under the sea. If either of those fail, you're left unable to communicate. Conversely, a car with a transceiver and antenna can continue communicating.
The other aspect to ham radio is precisely that is isn't easy or simple. It requires training, and self-learning to be able to make contacts, set up antennas correctly, and build transceivers. There is an element of luck about it too. Most of the global communication methods depend on solar activity. One day, you'll be able to easily communicate with someone on the other side of the world, and the next, you'll be hard pushed to contact someone over the border.
There are some ham radio communication methods that actually use the Internet: IRLP, Echolink, and AMPRNet to name a few.
Mobile phone are very useful too. Cheap, reliable, and easy to use. However, they use cables underground and under the sea for most of their range. Your mobile is only wireless to the nearest cell tower.
It might appear that there isn't much happening on ham radio due to the map. There are hundreds and thousands of QSOs taking place at any time around the world. However, only a fraction are logged (spotted) on the DX Cluster network. For instance, I have made 90+ contacts and only one of those was entered on a cluster. Also, only a small proportion of the logged QSOs contain location information that can be used to plot line on the map.
QSOs take place all over the world, all the time. However, some countries have higher populations, more free time, and are more likely to have a computer logger connected to the Internet
A QSO is the Q-code for a communication between two amateur stations.
The mode of a transmission is the way the information (voice, data, pictures, TV) is "encoded" on the radio wave. Examples used in broadcast radio are AM and FM. SSB (USB or LSB) and CW (morse code) are also very popular in amateur radio.
Propagation is the way the signal gets from the transmitter to the receiver. If close enough, the signal can travel directly (groundwave). Some frequencies can reflect off layers of the atmosphere (skywave). Other frequences can be bounced off meteor trails, aircraft, raindrops, or the moon.
Hams are given certain ranges of frequencies they can use. These are referred to, not by the frequencies, but by the length of the radio waves of those frequencies.
E.g. 300,000,000 (the speed of light in metres/second), divided by the frequency 20,000,000 (in Hz) is referred to as the 15 metre band. There are many bands available for ham radio operators.
A spot is a report of a QSO logged by an amateur on a DX cluster.
A DX cluster is a network of computers which share information about QSOs that are "spotted".
WSPR stands for Weak Signal Propagation Reporter. It's a mainly automated system that uses very weak signals to test global propagation. This data is skewed towards where the people are who use WSPR:
People around the world run software that listens for people using CW (morse code), or other digital modes. The software reports what callsigns it can hear. Often, a callsign will be heard by multiple skimmers at once. The skimmer also reports how well the signal was received (dB), and what speed the morse code was being sent at.
Licenced amateur radio users can use a wide range of amateur radio satellites.