"Trans-500" is a tag used in porn videos, and it refers to transgender content featuring five hundred or more scenes. Trans-500 tags signify that the video contains a large number of transgender-related scenes, which may include various combinations of TS (transsexual), TV/TVs (transvestite), TG (transgender), and other related themes. The tag is primarily used to help viewers find content that specifically features a larger variety of transgender themes and performers.
Please note that this explanation is for adult audiences who are familiar with the concept of transgender pornography, as it may not be suitable or comprehensible for minors or those new to this genre.