Titles are a part of language used to address people, which often also indicate the gender identity of the person being addressed. Common examples of titles include Mr. (traditionally male) and Mrs., Miss and Ms (all traditionally female).
Some titles are gender-neutral but indicate profession or societal standing, such as Doctor, Professor or President. However, these titles are only available to those with the relevant background, qualifications and/or employment. Other titles indicate both position and gender identity, such as Duke/Duchess in the aristocracy, or Brother/Sister in religious orders.
People with non-binary gender identities often wish to be addressed with a gender-neutral title. One example of such a title is Mx. which is used as a gender-neutral equivalent of Mr./Mrs./Miss/Ms. However, some situations where a title is required may not provide a suitable non-binary alternative, which is a form of misgendering.
In some places, titles are required to reflect legal gender, but in others titles are purely a social convention.