Original: Most cloth made for carom billiards tables is a type of baize that is dyed green, and is made from 100% worsted wool, which provides a very fast surface allowing the balls to travel with little resistance across the table.
Simplified: Most cloth made for carom billiards tables is a type of cloth called "baize" that is dyed green in color, and is made from 100% wool that has fibers that are made to be very straight (a process called worsted). Baize cloth provides a very fast surface allowing the balls to travel easily across the table material, called a "bed".