What is the incense Catholics use and why do they use it?
The first part of the question is the hardest…because there are thousands of different “flavors” or smells of incense. There are two primary divisions based on how they burn. One kind is ignited and burns by itself, this is common on incense sticks and other such items. The second kind does not burn by itself, and uses something else to keep it burning. In most of the Catholic Church liturgies you will find the second kind, which is placed upon some kind of burning charcoal in a container called a thurible. Centuries ago most incense came from two trees of the Terebinthian family, from India or Arabia. Incense was a very pricy commodity and usually only the very wealthy could afford it. Today it is made from numerous sources, and blended like coffee to provide certain aromas and flavors.
As to why it is used, the reason varies. The most ancient use was most likely to obscure the aroma generated by people who do not bathe regularly. When a crowd is gathered, the strong smelling incense was able to cover up the unpleasant odors with one more pleasing. Another purpose of the incense was to eliminate undesirable pests, such as mosquitoes. People today will use coils of citronella incense when outdoors for such purposes.
Many, if not most, religions employ the use of incense for various reasons. In Exodus Chapter 30 Moses was instructed to build an altar for incense, to offer a fragrance pleasing to God and as a way of purifying the environment. So for example as the priest incenses the altar or the gifts, it could be seen as purifying the sacred space used for the Eucharistic offering.
Incense is also seen as a way of eliminating other distractions so as to help one to focus in their meditation or prayer life. By providing a common smell, we are less likely to become distracted by the aromas that drift around us.
Incense is also seen as representative of our prayers rising up to God. For example in the funeral ritual near the end the coffin is incensed during a prayer that asks the angels to take the person to the bosom of Abraham. Leviticus 6: 15 refers to incense when it says “and he shall burn on the altar for a memorial of most sweet odor to the Lord”
While the Church uses incense liturgically we also recognize that smoke as a whole could be unhealthy as well, and that some people have allergic reactions to incense. Some incense claims to be “non-choking”, but I have found that to be questionable. I personally try to reserve its use for special occasions, such as Easter, Christmas, funerals, penance services, or events with the Bishop.