·Cost：The cost assigned to each step of the query plan by the CBO. The CBO worksby generating many different execution paths/plans for the same query andassigns a cost to each and every one. The query plan with the lowest cost wins.

·Card：Card is short for . It is the estimated number of rows that will flow outof a given query plan step.

·Bytes：The size in bytes of the data the CBO expects each step of the plan toreturn. This is dependent on the number of rows (Card) and the estimated widthof the rows.