French Fold just means that you fold the strip in half - lengthwise before sewing it to the edge of your quilt. Cut strips the width of your fabric and mitre the ends to join them into one long, continuous strip of binding.
It's probably what you've been doing all along - just new terminology. This method provides a double layer of fabric on the edges of your quilt. The edges are usually the frist thing to wear out on a quilt, so this helps extend the wear.