Explain Shuffling and Sorting in MapReduce?

Shuffling is the process of transferring the data. It transfers the data from the mappers to the reducers. The output data from the map is sent as input to the reducer. This process is necessary for the reducers or they would not have any input.

Sorting operation sorts the keys generated by the mapper. It is done to easily distinguish when a new reduce task should start. When a new key in the sorted input data is different from the previous, then a new reduce task starts.