The two parallel finished edges of the fabric are called the selvage. This edge will not ravel and has a tighter weave. It runs in the same direction as the straight of grain. Often it is a different color from the rest of the fabric. Sometimes the name of the fabric line and the colors found in the design are printed on the selvage.
Using the selvage in your quilt squares can cause problems as other fabrics may pucker after washing. (Most cotton fabrics will shrink when washed but the selvage has little shrinkage causing the puckers.)
Some quilters cut off the selvage as soon as they come home from the fabric shop. They want to make sure they don’t use this in their quilts. Others cut it off because they are collecting for a future quilt. In the last few years, quilts made from selvage strips have become very popular. (Yes, it does cause problems but lots of folks like a challenge!) Selvages can also be used as trims as seen below on the eyeglass cases.