In lightsaber combat, sequences were precisely choreographed series of attacks and parries. They were commonly used in practice to develop fast reflexes, though they were equally useful in live combat, where the fluid succession of attacks were far more useful than individualized moves.
In practice, sequences were used to help develop reflex and control in drills called Velocities. In these sessions, two sparring partners would repeat a single sequence of attack over and over again at ever increasing speeds until one was hit or conceded.
In live combat, some believed that using sequences in combat was superior to using individual moves, due to the inefficiency of taking the time to consider and apply single motions. In contrast, sequences were far quicker and more fluid, providing significant advantages. Each lightsaber form had its own set of sequences, and there were hundreds of different sets that could be applied to various combat situations.
Towards the end of the New Sith Wars, Sith Blademaster Kas'im instructed his students at the Korriban academy through sequences, many of which he designed himself, to ensure maximum offensive potential with a minimum of defensive exposure. On average, individual sequences took his charges two to three weeks of training and drills to master, and longer still if the sequence were derived from a form a student had yet to master.