It's not technically a liquid, but rather a thick, yellowish paste secreted by the beaver's castor sacs. These sacs are located near the beaver's anus and contain a mixture of oils, resins, and pheromones.
Castoreum was historically used as a trapping lure for its strong, musky scent, which attracts other beavers. However, its use has decreased significantly due to animal welfare concerns and the availability of synthetic alternatives.
Note: It's important to remember that castoreum is not a "liquid" in the typical sense. It's a viscous paste with a distinct odor.