It’s the agarwood you see on the market, or anything else. The old method of making incense was made by adding sandalwood and sandalwood powder with honey and other combustion-supporting materials; now it is mostly made of rosin wood and powder. Some add safflower and other traditional Chinese medicines to achieve medical value (aromatherapy), and of course there are other plants that add spices and combustion aids.
Supplement
There are two types of Taoist incense burning. One is that the master of the temple burns incense. In this case, standing incense is used. Three sticks are used as standard, which are inserted into the large incense burner. The spacing between three sticks in a row is considered to be no more than an inch wide, so there is a proverb "burning incense is no more than an inch, and the gods will not believe if it is too wide." Second, the owner of the altar holds incense. This incense is made of sandalwood. He is very particular about the length and thickness of each stick of sandalwood, which is no longer than an inch and not too thick. When the owner of the altar burns incense, the first stick of incense is inserted into the middle of the furnace, the second stick is inserted on the left, the third stick is inserted on the right, and the three sticks of incense are placed in parallel rows and close together. The left box of the incense burner contains incense noodles, and the right box contains sandalwood. Kowtow, kowtow ceremony, is the traditional etiquette of our nation. It has different respects and different rituals, and is expressed in different etiquette, so there is a nine-bow ceremony. [Qingfist and hands respectfully] is a sign of respect. In later generations, it evolved into kowtow as a salute. Until now, Taoism still practices kowtow as a salute. There are three types of kowtows and nine kowtows. In Taoism, one bow, three knocks and then another bow are considered a ritual. To congratulate the Supreme Saint Gaozhen on his birthday and celebrate the Taoist ceremony, three rituals and nine kowtows are required. Although a prayer mat is used for kowtowing, it is actually a matter of prostrating the five bodies to the ground, that is, the two feet and hands are on the ground. When kowtowing, the head and hands should be used. Stand with your feet in a figure-eight shape, with your knees and hands on the ground at the same time, your left hand hugging your right hand, with the palms of your hands facing downwards, forming a cross shape, with your body as one, expressing [eighty-one transformation].