Massed practice is the opposite of distributed practice. Massed practice is defined as a type of learning which has no intervals (or short intervals) and is presented repeatedly in a short period of time.
In distributed practice the material is to be learned over a sufficiently long time period. This ensures the success of the practice as the learner is able to retain or learn more.
On the other hand, in massed practice, the material is to be learned over a short time period. Though not as effective as distributed learning, massed practice has other uses. For materials whose knowledge need not be retained and which can be explained again when needed, massed practice can be used. Distributed practice can be used to learn items that are in the form of a list or a procedure.
For free and cued-recall, and for recognition, distributed practice is most effective.