The thurible is another name for a censer. It is used to hold a metal pan in which heated charcoal can be carried. The charcoal is sprinkled with incense at various times during the liturgy to create perfumed smoke. Incense comes in the form of powdered or granulated gums or resins obtained from various trees.
The apertures in the thurible cover allow the smoke to escapeand keep the charcoal burning as the thurible is swung to and fro.
The use of incense in Christian worship is of great antiquity (at least the sixth century if not earlier) and is widespread. It is seen as being a symbol of prayer rising to the Lord.
In the Mass, incense is typically used during the entrance procession, to cense the altar after the procession, in the gospel procession and during the reading of the gospel. It is then used after the offertory to cense the offerings, the altar, the ministers and the people before censing the elevation of the host and the chalice at the consecration. Incense is also used at other services, e.g. during the Magnificat at Evening Prayer on Sundays.