The Digital World is a fictional universe featured in the Digimon media franchise. In Digimon anime, manga, video games, and other related merchandise, the Digital World (or DigiWorld for short) is a parallel universe to Earth that was made from computer data originating in Earth's communications networks.
According to the video game Brave Tamer, the Digital World's beginnings can be traced to the early twentieth century, with the activation of the Atanasoff–Berry Computer (ABC)—the first computer—which laid the basic foundations of the world. Subsequently, the first patented computer, ENIAC, was activated, and proceeded to build upon those foundations, shaping the Digital World. Over the ensuing years, through the continued growth of the electronic communications network on Earth, the Digital World continued to expand and grow, even after the ABC and ENIAC were shut down. There are multiple alternate reality incarnations of the Digital World, each one running parallel with the various multiple Earths that exist in the multiverse.
The different Digimon anime series are set in separate Digital Worlds. The basic mechanics, locations and inhabitants of Digital World appear in each, though the individual natures, origins, and histories of the worlds vary greatly. Similarities between the various Digital Worlds exist, however. They all basically parallel Earth's geographic features. There are continents, islands, deserts, mountains, oceans and almost all other kinds of terrain one finds on the topography of Earth. However, as data is easy to modify, and considering that the Digital World is made up of data, the features of any particular area of DigiWorld are subject to immediate and drastic alteration at any time. For example, a gigantic mountain can be formed in moments or portions of islands can be scattered across a sea with ease. The malleability of the Digital World makes it a frequent target of attack from within and from humans with malevolent intentions.
Although ordinary animals like birds and fish are known to exist in at least some of the Digital Worlds, the dominant lifeforms of all realities are Digimon. Digimon are sentient creatures that, like the Digital World, are made of data. It is possible for Digimon to travel to the "Real World," what Digimon call Earth, though this requires the opening of some sort of dimensional wormhole in Digital World.
Most of humanity does not know of Digital World's existence. The few humans that do either programmed some aspect of the original version of that world or were summoned there by a Digimon or another digital being. On rare occasions, however, a wormhole can appear on Earth, allowing people unknowing of the Digital World to enter it.