This porn video tag refers to a "transsexual" or "TS" category. Transsexual content typically involves transgender individuals, specifically those who have undergone or are in the process of transitioning from one gender to another through hormones and/or surgeries. This can include pre-op, post-op, or non-operative transsexuals. These videos often depict scenes with transsexual performers engaging in sexual activities with other men, women, or both.