Ham radio requires from its devotees, to experiment with various technical aspects, like electronics, antennas, etc.
Each radio amateur is identified by a unique callsign, which comprises of a special country designator (for example, for Greece this designator is the letters 'SV') , then a number (which may designate a particular area within the country) and then a 2 or 3 letter suffix, which uniquely identifies the amateur, within his country. For example, this author is SV1CEC, which means that he is a Greek radio amateur (SV), living in the greater Athens area (1) and his unique code is 'CEC'. The callsign is an absolute identification of his bearer. There are thick books, called callbooks, which show information for every ham on earth.
Radio amateurs use a variety of radio frequencies for their communications and experiments. Some of these frequencies are :
High Frequency (HF) 1.830- 1.880 MHz 3.500- 3.600 MHz 7.000- 7.100 MHz 10.000-10.150 MHz 14.000-14.350 MHz 18.068-18.168 MHz 21.000-21.450 MHz 24.890-24.990 MHz 28.000-29.700 MHz Very High Frequencies (VHF) 50.000-54.000 MHz 144.0 - 146.0 MHz Ultra High Frequencies (UHF) 430.0 - 440.0 MHz 902.0 - 928.0 MHz 1240 - 1300 MHz
These frequencies are for Europe, while in other parts of the world they might differ slightly. If you happen to have a radio capable of receiving the HF bands, tune towards the lower part of these bands and you will probably hear the sound of Morse signals used by radio amateurs.
Hams are also in the forefront of technology. Communications are not limited to direct communications between two amateurs. Hams are also using satellites which act as repeaters and enhance the range that can be covered by a station. They even communicate with each other, by using the moon, as a reflector (which is call EME, or Earth-Moon-Earth contact).
Radio Amateurs are also known for the help they provide to the community, in various instances of natural disaster. They provide an efficient and well-organized communications network, capable of handling large ammount of transfered information. It is not rare for ham operators to help the state forces in earthquakes, hurricanes etc.
As it was expected, radio amateurs were among the first to use personal computers for their tasks, and several of them have formed a wireless network, which is part of Internet (the .ampr.org domain, or ip addresses in the 44.xxx.xxx.xxx schema). The original pages that you see here, are from this network, specifically from sv1cec.ampr.org, one of the three nodes of this network in Athens, Greece.
If you want to read some more things about Amateur radio, check the ARRL's equivalent document.