The tag "postoptrans" can be interpreted as follows:
Post-operative transformation or post-op trans, refers to the category of porn videos featuring individuals who have undergone gender reassignment surgery. In these videos, a person who was assigned male at birth may now identify as female and vice versa. The "post-op" part refers to after their surgery (operation) and the "trans" part stands for transsexual or transgender. These types of videos often showcase intimate scenes with the individual's new body, reflecting their true gender identity.