Bees coat almost everything in the hive with Propolis to protect themselves from disease - propolis is also very sticky and will stain like iodine so don't place it on a countertop, etc. without having something underneath it to protect any surface.
Bee Propolis is gathered by bees from the leaf buds or bark of trees. So far 17 chemical substances in propolis have been described, some of which are: cinnamic acid, vanillin and an aromatic unsaturated acid characterized by antibacterial effects on certain gram-positive and gram-negative micro organisms.
For honey bees, propolis is used as a kind of glue. They use it to seal cracks and crevices in the hive to make it less drafty when it is cold. Propolis is sticky when it is warm and it is difficult to deal with when it is hard.