Seam allowance is the area between the edge of the fabric and the line of stitching. It is essential in sewing because it provides extra fabric to secure the seams and allows for adjustments. Common seam allowances range from 1/4 inch to 5/8 inch, depending on the type of project and fabric used. When cutting fabric, it's important to include the seam allowance in your measurements. This ensures that the final garment or item fits properly. Proper seam allowance helps maintain the integrity of the seam and contributes to the overall quality of the finished product.