What is the difference between a sheepskin rug and a lambskin rug?

A lambskin rug is from a sheep that is less than 12 months old and has not developed incisor teeth. The wool has generally not been shorn by the farmer and still has the original soft wool tip (this is often referred to as baby wool). Sheepskins are from sheep that are older than 12 months and have developed incisor teeth. The two terms are commonly used interchangeably.