Katas are an integral part of Karate training. The martial artist follows a particular sequence of movements that include the attack and defense against one or several imaginary attackers.
Practicing Kata is a good way of exercising the pure form of techniques. Many Katas also contain secret or hidden Karate techniques that are not obvious to the unsuspecting bystander (and often not even to the student performing the Kata).
Katas are a means of maintaining the true form of an original style, and its tradition from master to student, who may then in the future teach his own students. The meaning and application of techniques found in Kata is called Bunkai. As the student progresses through the ranks, more and more Katas and the techniques contained therein are mastered.
Therefore, Katas are also an important aspect of the grading procedure, where student undergo an examination process that culminates in the award of a belt whose colour indicates the achieved skill level of a student.