Quirks come in a wide variety; as the name Quirk implies, they are unique to each individual. However, Quirks can be divided into categories based on what they do and how they function, known as Quirk Types. Some Quirks cause a permanent physical abnormality to the user's body, known as Mutant-type. Some cause the user's body to undergo a temporary physical abnormality when the power is used, known as Transformation-type. Finally, some quirks don't cause any abnormalities to the user's physical body at all, and they are known as the emitter type.

Aside from the three Quirk Types, Quirks can also be categorized into Sub-Types. A Quirk can fall into a given sub-type regardless of its type. In other words, a given sub-type can be designated to Quirks of all three types, so long as the Quirks possess an aspect that fulfills the requirement to be considered as part of that sub-type.

Emitter

Emitter type (also called Operative) Quirks are abilities that allow the user to generate and possibly control certain things or alter existing things around them in specific ways. The emissions of Emitter-type Quirks can have a wide variety of properties and abilities. Emitter-type Quirks can also have various ranges. While some users require physical contact to use them, others can have much longer ranges with no distance restrictions.

While most Emitter-type Quirk users generally have a handle on their own "emissions," it's also possible for users to hurt themselves by coming into too much contact with their Quirk. In the case of generating substances, making too much too fast or for too long can harm the user as they are using reserves from their own body or gradually lose their natural resistance to their own harmful Quirk.

Some Emitter-type Quirks cause the user's body to take on a temporary alternation. While such Quirks would normally fall into the Transformation class, the difference is that these powers require the user to take in an outside resource in order for the Quirk to activate.

Transformation

Transformation-type (also called Composite) Quirks are abilities that cause the user to take on a temporary alteration of some kind. Transformation-type Quirks allow the user to temporarily "transform" their body in a variety of manners, sometimes enhancing existing features, removing features, or adding new features to the body altogether. Transformation-type Quirks usually require a conscious effort by the user to "activate," though most users can be trained to initiate them reflexively, depending on the conditions necessary for activation and practice to initiate their Quirks with greater intent and precision

Transformation-type quirks usually require close-range proximity in order to fully utilize them in combat because they only affect the user's body. While Transformation-type Quirks are often quite powerful, their biggest weakness is that their effects are often temporary, and over-exertion usually leads to negative repercussions on the user's behalf. Transformation Quirks can also be limited based on the user, how resilient their body is, and their available resources. Some users condition their bodies in certain ways to operate their Quirks more effectively.

Transformation-type Quirks are the only known type of Quirk that can bestow the user attributes they do not normally exhibit by default. Because this type of Quirk combines the activation time and mutant-shape aspects of the other Quirk types, it is also often known as the Hybridor Composite.

Transformation seems to be the least common type of Quirk.

Mutant

Mutant-type (also called Heteromorphic) Quirks are abilities that cause the user a permanent "abnormality" directly related to their power. Mutant-type Quirks create bodily structures that grant the user more complex abilities that Emitter and Transformation Quirks cannot safely provide. Often, they will bestow prehensile appendages that the user can control or add structures to pre-existing limbs to enhance pre-existing abilities. Mutant-type Quirks even have the ability to channel certain aspects of their user through them in a similar manner to Emitter-type Quirks.

Mutant-type Quirks are also the only known type of Quirk that can be passed down through generations without necessarily bestowing the corresponding ability. As a result of this, while it's uncertain how common Mutant-type Quirks are, it can be safely assumed they are the most commonly inherited. While not necessarily a weakness, Mutant-type Quirks cannot be turned off and sometimes cause inconvenience to users due to their malformations.

Users with Mutant-type Quirks, most often known as "heteromorphs," also find themselves the most discriminated against, even by other Quirk users, due to their outer appearances. Sometimes they are pushed toward villainy due to the prejudices they deal with due to their looks. Cults such as the Creature Rejection Clan also exist with the purpose of eradicating these heteromorphs.

Source:
https://myheroacademia.fandom.com/wiki/Quirk