Taper is the difference in width between your board's nose and tail, measured in millimeters. A board with a wider nose and narrower tail has more taper, which naturally sinks the tail and lifts the nose in deep snow—giving you better float in powder.
If you mainly ride park or love riding switch, look for little to no taper (0–5mm). Twin-shaped boards with zero taper ride the same in both directions. For all-mountain and freeride riders who chase powder but still cruise groomers, moderate taper (6–15mm) is the sweet spot—you get noticeably better float without giving up hardpack performance. Dedicated powder boards often have 16mm or more of taper for maximum float in bottomless snow.
Don't assume a tapered board can't handle groomers—moderate taper works just fine all over the mountain. The real tradeoff is switch capability: more taper means the board is designed to go one direction, so switch riding feels noticeably off.