The key feature of the Tamagotchi is that the pet needs to be "cared for" - fed, played with etc. Failure to look after it will alter its mood and ultimately it can die (or, euphemistically, "return home"). The way in which the virtual creature is treated also affects its development and ultimate form. This need for constant care and attention makes the game very addictive for younger children.
Tamagotchis have received both praise and criticism from adults. On the one hand the need to care for their virtual creature is said to teach responsibility. On the other hand their addictive nature has resulted in many school classes etc being disrupted because children were constantly checking up on their pets.
The derivation of the name Tamagotchi is usually given as a combination of the Japanese words for "egg" ("tamago") and "friend" (tomodatchi"). An alternative is the combination of tamago with the Japanese word "chi" which means cute and loveable.
Since 1996 there have been a large number of different Tamagotchi versions. Perhaps the most significant was the launch in 2004 of the Tamagotchi Connection - (the English language version of the Japanese "Plus" model). This included an infrared communication facility to allow different Tamagotchi to interact. 2005 saw the release of the Connection V2 which added Gotchi Points (GP) which owners could earn and spend in a "virtual shop" to buy virtual toys etc. Connection V3 was released in 2006 and - as well as being available to buy in a variety of cool colours - added support for codes generated by the online Tamagotchi Town (Tamatown).
At the time of writing the latest Tamagotchi version available to buy in the shops is the Connection V4. This has a separate Tama Town to the V3 model.