If you take a yard of fabric, cut it into two half yard lengths (18" by width of fabric "WOF") then open one of the half yard pieces so the material lays flat on a cutting surface; and cut it smack dab down the center on the fold line (parallel to selvage), you'll have a FAT QUARTER, or "FQ" for short. A fat quarter used to be 18" x 22" but with fabric width more common at 42", a fat quarter would be 18" x 21"

Why use them? A FQ is still a 1/4 of a yard, but instead of being a skinny 9" x 42", it's a squarer shape of 18" x 21." You can cut larger chunks of fabric than would be possible from a typical 1/4 yd cut. You get a dozen 5 inch squares, or "charms" from a FQ, but only 8 if you cut the charms using a 1/4 yard piece 9" x 22." There's lots of quilt patterns, such as our Yellow Brick Road pattern, which use fat quarters. Build your material stash with FQ's since they generally are less expensive to purchase by the piece and still have a great variety of colors/themes.