Beginning quilters often have difficulty in understanding fat quarter cuts of fabric.

A fat quarter is made by cutting a yard of fabric into four equal parts.  One yard of quilting fabric measures 36" x 44"; if you cut this into four equal parts then each measures 18" x 22".  While a straight 1/4 yd cut mearues 9" x 44", quilters generally prefer to buy fat quarters rather than quarter yards as this gives more flexibility in cutting for applique or large blocks. 

Two fat quarters equal 1/2 yd and four fat quarter measure 1 full yard.

Buying fat quarters is a great way to add to your stash of fabrics.  There are many great quilt books that specialize in fat quarter projects.