Seam allowance refers to the extra fabric that is added to a garment or sewing project as a buffer between the raw edges and the finished seams. It typically ranges from 1/4 inch to 5/8 inch, depending on the type of fabric and desired finish. The purpose of seam allowances is to provide room for error during construction, such as uneven sewing or shrinkage after washing, while also allowing for ease of movement when wearing the garment. Seam allowances can be trimmed away after seams are stitched, but it's important not to cut too close and risk damaging the integrity of the finished seam.