"Tren" in the context of a porn video tag is likely referring to the term "TREN" which stands for 'Threesome Real Extra Nasty.' This tag indicates that the content features a threesome scene, typically involving three individuals engaging in sexual activities. This can include a variety of combinations like two men and one woman, two women and one man, or all three participants being of the same gender. The "Real Extra Nasty" portion emphasizes that this is an explicit, uninhibited threesome encounter.