Multilevel Feedback Queue Scheduling (MLFQ) CPU Scheduling is like Multilevel Queue(MLQ) Scheduling but in this processes can move between the queues. And thus, much more efficient than the multilevel queue scheduling. 

In a multilevel queue-scheduling algorithm, processes are permanently assigned to a queue on entry to the system and processes are not allowed to move between queues. 

As the processes are permanently assigned to the queue, this setup has the advantage of low scheduling overhead, 
But on the other hand disadvantage of being inflexible.

Multilevel Feedback Queue Scheduling (Operating System) : https://www.geeksforgeeks.org/multilevel-feedback-queue-scheduling-mlfq-cpu-scheduling/