Information from the Digimon Wiki....

Digimon are fictional creatures from the Japanese Digimon media franchise. They are
central to several anime series and films, manga, video games and other merchandise. The word "Digimon" is invariable in the plural, and stands for "Digital Monster". Digimon include almost all the creatures that reside within the fictional parallel universe called the "Digital World." There are many different species of Digimon, as well as unconfirmed and new generations of Digimon yet to be revealed. The rate of new Digimon species continuously increase as the Digital World expands each year.

Digimon hatch from eggs called Digi-Eggs. They age via a process called "Digivolution" which changes their appearance and increases their physical powers. Some Digimon act feral, like wild animals. Most, however, possess human intelligence, speech, and personality traits. It was mentioned that, if a partner Digimon were to be separated from their partner, then they would start to become weaker. An example of this is Yolei Inoue's partner, Poromon. When Yolei is away in Kyoto, Poromon begins to feel weaker each day.

The first Digimon anime introduces the Digimon life cycle: they age in a similar fashion to real living organisms, but do not die under normal circumstances because they are made of reconfigurable data. Old Digimon and Digimon who receive fatal wounds dissolve into infinitesimal bits of data. The data then recomposes itself as a Digi-Egg, and the Digimon goes through its life cycle again. Digimon who are reincarnated in this way will sometimes retain some or all their memories of their previous lifespan. However, if a Digimon's data is "downloaded" as demonstrated in Digimon Tamers, in which all the data of a dying Digimon is absorbed by another, or if the data is completely deleted or destroyed, as happens in Digimon Data Squad, it will permanently die. In special cases, some Digimon do not get reincarnated despite their data still existing. A famous example is the Wizardmon in Digimon Adventure, whose data remains in the Real World following his death and thus is not reconfigured.