A microlabel or subcategory is an identity that falls under the umbrella of a larger identity and cannot stand on its own. For example, an apothisexual person is someone who is asexual and sex-repulsed. If someone says they are apothisexual, it is also implied that they are asexual, because apothisexual is a modifier, making it a specific sub category of asexuality. Microlabels are most often used to describe more specific feelings, and to create a sense of community for people who also experience those feelings. A microlabel is designed to be like a stand to someones identity: it is needed, but it cannot stand on its own.
Unlike what some people believe, the term microlabel has nothing to do with how popular or well known the identity in question is. There can be uncommon terms that are not microlabels, because they can stand on their own and do not modify an existing identity. There can also be microlabels that are well known and popular, but they are still microlabels because they are a subcategory of an existing identity. An uncommon, niche, and not well-known identity would be a pocket identity (see pocket sexuality and pocket genders).
It has been used by the MOGAI community in the social media platforms Tumblr, and Reddit. It also has been used by neurodivergent people and others to help them express their gender and sexual identity.