Rag quilts are a type of quilt where the seams are fringed on the front of the quilt.  The back is smooth like a regular quilt.  Here are some things to consider when buying a rag quilt:

Fabric: Rag quilts can be made of cotton, fleece, flannel, and chenille.  Each fabric has its own texture and weight, so keep that in mind.

Batting: Some rag quilts have batting sewn in the middle layer.  I personally prefer not to have batting unless the rag quilt is made of cotton.  Batting makes the quilt warmer and heavier.

Size: Rag quilts can be any size, so make sure you know the dimensions of the quilt before you purchase!  A good size for a baby is around 36" x 40".

Kits: If you are interested in making your own rag quilt, consider buying a kit which will have the coordinating fabrics and instructions included for you.  They are fairly easy to make -- and very fun.