An intersex person has sex characteristics e.g. sexual anatomy, reproductive organs, and/or chromosome patterns that do not fit the typical definition of male or female. This may be apparent at birth or become so later in life e.g. puberty. Intersex people, just like dyadic people, may identify with any sexual orientation or gender identity.
Being intersex is often treated as a medical disorder which should be corrected with treatments such as hormone therapy or surgery to "normalise" sex characteristics. If an intersex condition is discovered at birth or during childhood then medical procedures may be performed without the child or parent giving consent or even being aware, and many intersex people are not notified of their condition even as adults. Because of this culture, the intersex community often denotes assigned sex using the terms CAFAB and CAMAB, standing for Coercively Assigned Female/Male At Birth.
A transgender-intersex (trans-intersex) person is an intersex person whose gender identity does not match the one decided on by their doctors and/or parents at birth, and identifies as transgender and intersex at the same time. Not all intersex people who are identify as trans-intersex, however.
Being intersex is not to be confused with being non-binary - the former is based on both identity and physical variations on the typical definition of male or female, while the latter is purely a gender identity.