Myrrh is a sap-like substance (resin). It is extracted from a number of small, thorny tree species of the genus Commiphora. One can easily find them in Northern Africa and Middle East terrain, but it can be found in some western countries too.
This resin actually comes out of cuts in the bark of trees with a sweet, and smoky aroma. It has been used throughout the history as a medicine. Even in biblical times, it was used as a spice and natural remedy. In fact, in the New Testament, it's been mentioned that it is one of three gifts which three Wise Men brought to Jesus (PBUH).