A slipmat is a circular piece of slippery cloth or synthetic materials disk jockeys place on the turntable platter instead of the traditional rubber mat. Unlike the rubber mat which is made to hold the record firmly in sync with the rotating platter, slipmats are designed to slip on the platter, allowing the DJ to manipulate a record on a turntable while the platter continues to rotate underneath. This is useful for holding a record still for slip-cueing, making minute adjustments during beatmatching and mixing and pulling the record back and forth for scratching. They are also very commonly used simply as decoration for when a record isn't on the turntable.
Slipmat for your record player/turntable platter