It is a cloth placed on an altar.
As long as it takes to learn the proper procedures. Many parishes have training programs for altar boys. Check with yours.
A dedicated Catholic Church has an altar and both the altar and the Church itself have been solemnly consecrated with a lot of Sacred Chrism and incense by a Bishop. There will be a signed declaration somewhere that says that the Bishop has consecrated the Church and when.
the Sanctuary
Roman Catholic AnswerThe altar (and the priest when he is at the altar) are contained in the sanctuary of the Church.
The sanctuary is the part of the church which contains the altar.
An altar bell is a bell rung in the Roman Catholic church at significant times during the Mass.
It is the table at the front of the church, usually made of wood or marble. It is where the Eucharist is celebrated.
White! The color of Joy!
A Catholic Church has as its main focus a Sanctuary which contains an Altar, Ambo, and the Tabernacle which are all used in the Celebration of the Most Holy Mass.
.Catholic AnswerNormally stone, at least the actual part of the altar that the sacrifice is celebrated on would be stone. There is often an "altar stone" inserted in the top of a wooden altar.
It is possible for a Catholic church to have a relic, such as a bone, of a saint placed within the altar. This practice is done to honor the saint and to strengthen the spiritual connection between the church and the saint.