Indian incense divides into two forms and confusing them makes the literature hard to follow. Dhoop is the older: a resin, or a paste of resins, gums and powders, burned on charcoal or moulded into a cone that burns on its own. Agarbatti is the stick, in which the aromatic paste is rolled onto a thin bamboo splint, and it is a comparatively recent industrial product.
The bamboo core matters. It is why a stick of agarbatti smells partly of burning bamboo, which is a note the older forms do not have, and why practitioners who care about the material tend to prefer dhoop or a solid stick with no core. Japanese and Tibetan sticks are made without a splint for that reason.
The compounded pastes rest on a binder. Makko, the bark powder of Machilus thunbergii, is standard in Japan and increasingly elsewhere; halmaddi, an oleoresin from Ailanthus triphysa, was the traditional Indian binder and gives the soft honeyed quality that older Nag Champa is remembered for. Halmaddi supply collapsed from overtapping and the substitutions that followed are why the modern product smells different.
The industry is large and largely informal: hundreds of thousands of people, mostly women, rolling sticks by hand at piece rates, concentrated in Karnataka and Tamil Nadu. It is an offering, a household smell and a rural livelihood at once.