Absinthe is a high proof spirit flavored with anise, wormwood, and other herbs. It has an interesting legal history, but since the early 21ˢᵗ century, it has been legal throughout the world. Statements of its hallucinogenic effects are exaggerated; modern absinthe will not cause any sort of hallucinogenic experience. Whether older absinthes caused such effects is likely a matter of embellishment or questionable production methods.
French verte absinthe is the most famous as it is the quintessential green absinthe. It is also the absinthe that is generally called for on this blog. Absinthe enthusiasts exist online to help better guide purchasing choices, but generally speaking try and stay away from artificially colored neon green absinthes. There are many vivid green absinthes that do not rely on food dye.
Throughout most of the 20ᵗʰ century, absinthe was substituted with pastis or other anise-flavored liqueurs.