Evolution

Evolution is the ability of a Digimon to develop into a more powerful creature. While it can occur naturally, Contracted Digimon are able to access it much faster, and have more versatility since they are connected to a Human through a Digivice.

If a Digimon suffers sufficient damage levels, even a Naturally-Evolved Digimon will devolve to a lower form. Depending on the amount of damage taken, they may even revert to a Digitama. Devolution can be forced through the Digivice.

Types

Natural

The Natural Evolutionary Line a Digimon would follow if not Contracted. All Digimon have the potential to reach Ultimate Level, but it takes a long time and a great amount of Light of Evolution to reach each new Evolutionary Plateau. Those who do are usually referred to as "Naturally-Evolved", such as Yamainumon being a "Naturally-Evolved Adult".

Levels
Digitama	(Digi-Egg)	Digitama is the state all Digimon start their Evolution in. It is an egg in which their code and core are kept protected. If a Digimon's Signal is scanned while they are in this form, the Digitama is destroyed and does not return to Primary Village.
Baby-I	(Fresh)	Once a Digimon has enough energy to emerge from its Digitama, this is the first form it will take. Very much a newborn/baby-like form, it usually has limited if any speech and generally only one, weak attack to defend itself.
Baby-II	(In-Training)	The second form of a Digimon, it remains extremely childish in intellect and capability. The equivalent of Digimon "children", Baby-IIs are not usually allowed outside their home villages; some do not even depart Primary Village until they reach Child Level.
Child	(Rookie)	This is the Level which the most Digimon are found, and the level at which most Digimon remain at the longest; Contract Digimon often use Child as a default evolutionary form, as it lacks the disadvantages of Baby-II, but also lacks the Light of Evolution demands of Adult Level. Despite its name, Child Digimon are generally considered late adolescent-to-full adult in Digimon society.
Adult	(Champion)	The second most common level, Adult is the level at which most Evolutionary Lines tend to diverge and show the most variation, even in Non-Contracted Digimon. It's considered the "workhorse" Evolutionary Level; it's when a Digimon truly starts to process Light of Evolution and emit it from within their Core. Adults are universally considered just that in Digimon society, and generally are when a Digimon becomes capable of holding their own in battle.
Perfect	(Ultimate)	Somewhat of a transitionary level between the simple combat readiness of Adult and the absolute power of an Ultimate, Perfect Digimon are somewhat rarer, especially when compared to Adult or Child-Levels, and use a large amount of LoE in order to evolve and to maintain their forms. They are all somewhat unique existences, but they lack the sheer power and singular nature of an Ultimate.
Ultimate	(Mega)	The highest natural evolution. Groups that are all Ultimate Levels are: Zonemasters, Royal Knights, Demon Lords, and the Olympus Twelve.

Alternative

These are Evolutions usually found only in Contracted Digimon.

Evolutions
Armor Evolution	Requiring a Digimental, an Armor Digimon is slightly weaker than a true Adult, and their Charge Ups and Final Charges are only 60% as powerful as regular ones. However, these forms lie outside of the normal Evolutionary Line and do not have an Evolution Timer to limit their use.
DigiXros	(Define DigiXros)
Jogress	(Define Jogress)
Blast Mode	(Define Blast Mode)
Hacked	Through use of a 'Hacking Signal', the Crowns are able to evolve their partners to any form in their evolutionary line, up to Perfect Level.

Tools

These are items or objects that are required for evolution of some sort.

Digivice

The Digivice is required for basically all types of Evolution.

Digimentals

An active Digimental will grant an Adult-Equivalent Evolution.
A DigimentalPlus/Digimental+ will grant a Perfect-Equivalent Evolution.
A DigimentalFinal has the capability of creating an Ultimate-Equivalent Evolution.

Circuits

Circuits are required for Perfect Evolution.