Charm Packs are 5 inch squares containing fabrics from a specific collection or coordinating quilting fabrics. There are 42 squares in 1 charm pack. These pre cut squares allow the quilter to have a great selection and reduce cutting time. Many quilting patterns require 5 inch squares.
The advantage is you are buying a great selection of different prints of this size.
What can you do with a 5 inch square? Make half square triangles, 4 patch blocks, make easy corner triangles, even pieced charms that measure 4.5 inches by 4.5 inches. To make the half square triangle: Draw a diagonal line on the wrong side. Sew 1/4 inch on each side of the line, cut apart, press open, makes 2.
The importance is the accuracy of the cuts you receive. This is the time saver for the user. They are packaged by the manufacturer or custom made by the seller.