Could you please educate me on herbal incense?

Herbal Incense: You might be referring to synthetic cannabis or marijuana, also known as "spice." it's a synthetic designer drug where unidentified herbs are sprayed with unquantified amounts of synthetic cannabinoids. It's a dangerous drug because, like with marijuana, it can precipitate psychosis -- and also you don't know what you're getting. Designer drugs are made to evade laws against them.