What Is Progressive Discipline?
Progressive discipline is a managerial tool that involves applying various consequences, tied to performance in a progressive way (from less significant to more significant), to encourage employees to improve their performance or move the process along so that the impact of poor employee performance is reduced or eliminated.
(adapted from Manager's Guide To Performance Reviews, by Robert Bacal, p. 186)
In simplest terms it involves communicating with the employee that there is a problem, and specifying the details of the problem, setting and communicating what will happen if the problem is not resolved, and then invoking the consequences if the problem is not resolved.
The idea behind progressive discipline is to provide an opportunity for the employee to improve. It is not a method of punishment.
See also: Progressive Discipline For Addressing Performance Problems