What is a seam ripper used for?

A seam ripper is used to take seams out of materials. Like say for example I wanted to make a quilt out of several different materials, so i would sue a seam ripper to take apart them materials to make the quilt.

A seam ripper is used to cut the threads that hold the pieces of fabric together.

You use a seam-ripper to remove stitches in a fabric without tearing the fabric, instead of scissors or something else. Generally you use a seam ripper and hook it into the stitch at the seam, in order to be able to go back and re-sew the area without damaging the material. :D