Kata (literally: “form”) is a Japanese word describing detailed patterns of movements practiced either solo or in pairs. Karate Kata are executed as a specified series of a variety of moves, with stepping and turning, while attempting to maintain perfect form. The practitioner is counseled to visualize the enemy attacks and their responses. Karateka “read” a kata in order to explain the imagined events. There are perhaps 100 kata across the various forms of karate, each with many minor variations.
Traditionally, kata are taught in stages. Previously learned kata are repeated to show better technique or power as a student acquires knowledge and experience. It is common for students testing to repeat every kata they have learned but at an improved level of quality. The student will perform one new kata and one or two previous ones, to demonstrate how much they have progressed.
The various styles of karate study different kata, or variations of a common core. Some kata may therefore be known by two names, one in Japanese, the other in Okinawan/Chinese. This is because Gichin Funakoshi renamed many kata to help Karate spread throughout Japan.
[Source: Wikipedia. More here]