Basic Information
A censer is a vessel designed for the burning of incense.
Censers come in a variety of shapes and sizes from small, hand-held devices that double as hand-warmers (popular in Tibet and the North of China) to huge pieces used in temples. A censer designed to hand from chains is sometimes known as a thurible.
These devices are useful for any purpose for which incense is typically burned - religious ceremonies, domestically (to cover up bad smells), medicinally (for aromatherapy or to ward off "bad airs") or as a ritual tool where they will typically represent the element of air. Given the purifying and sanctifying aspects of incense use, a case might be made for using censers in ward magic - but if your warding incense happens to contain citronella, then your ward against insects might turn out not to be all that magical.
Censers are usually decorative and may constitute treasure - materials of construction can be anything relatively fire-resistant, including metal, ceramics and even hardwood.