This tools really comes in handy if you have any skipped stitches. Occasionally (!) this can happen and rather than re-sew the line this tool has a fine point that allows you to push the stitch into the fabric hiding the fact it skipped.
Use it to hide any stray threads on your quilt. Highly recommended by quilters like Cindy Needham.
To pull a loose thread into your quilt go in from the back to the front or from the side and pull the thread into the quilt sandwich using the very fine crochet style of hook.