Tie-in and Tie-off are small groupings of stitches at the beginning and/or end of embroidery elements. Their purpose is to lock the thread in place and prevent it from pulling out when the machine starts sewing or trims. Setting tie stitches appropriately for the design will help keep the design running smoothly as well as stay in the garment after laundering.
For more information please see the DesignShop v11 manual.