How to Sew: 'Right Sides Together' / Creating hidden seams
When you sew two fabrics together, you usually don't want to be able to see where you've sewn when the item is finished.
To keep seams hidden on the inside, often you'll be asked to sew your fabrics 'right sides together' and turn them inside out. The side of the fabric that you want to be visible in your finished product is called the 'right side.'
When you sew 'right sides together,' you join the fabrics together with 'right sides' touching. If you're sewing a rectangular or square product, like a cushion or a pillow case, or if you're sewing lining, wuite often you'll be required to only sew along three and half out of four sides of the square/rectangle. Then you reach into the gap where you didn't sew up and turn the fabric inside out.