The Digimon Virtual Pet was a toy, released in 1997 by Bandai. What became a TV series, toyline, comic, cardgame, and more began as the simple concept of a Tamagotchi for boys (as Bandai was also the creator of the Tamagotchi). It was similar to earlier virtual pets ("v-pets"), with the distinctions of being much hardier and being able to connect to fight other Digimon v-pets. Every owner would start off with a baby Digimon, train it, take care of it, cause it to evolve, and then have battles with other Digimon owners to see whose was stronger. The Digimon pet had several evolution capabilities, so two owners could have wildly different Digimon.

Source: Wikipedia