Final answer:
An IdentityMapper reads input data and emits key-value pairs as is, while an IdentityReducer receives intermediate key-value pairs from mappers and emits them without any changes.
Step-by-step explanation:
IdentityMapper and IdentityReducer are classes in the MapReduce framework. They are used when the input and output keys and values of a MapReduce job are the same. The IdentityMapper class reads the input data and emits key-value pairs as is. It is the default mapper in MapReduce. The IdentityReducer class receives the intermediate key-value pairs from the mappers and emits them without any changes.