A forked (or split) tail has two prongs at the back of the board—think of it as a milder version of the deep V-shaped swallow tail you see on surf-inspired powder boards. The split lets the tail sink into soft snow, which naturally lifts the nose and boosts float in powder.
The real advantage over a full swallow tail is that you keep more surface area at the back, so the board holds up better on hardpack and groomed runs. It's a solid middle ground if you want that surfy feel in fresh snow without giving up too much stability when conditions firm up.
This shape makes the most sense on directional freeride boards for riders who regularly chase powder but still need to get down hardpack to reach the next stash. If you mostly ride resort groomers, park, or don't see deep snow often, a standard pointed or blunt tail is the more practical choice.