resin from Boswellia trees

Frankincense is an aromatic resin used in incense and perfumes. It is obtained from trees of the genus Boswellia in the family Burseraceae.

Frankincense from Yemen

Frankincense is tapped from the scraggly but hardy trees by striping (slashing the bark). The resin then bleeds out and hardens. The hardened streaks of resin are called tears.

One of the gifts brought by the Three Wise Men, along with myrrh, which is pretty much the same kind of thing.