Why Spark is faster than MapReduce?
The main difference between Spark and MapReduce is that Spark processes and retains data in memory for subsequent steps, whereas MapReduce processes data on disk.
Instruction: Why Spark is faster than MapReduce?
Context: 
Response: The main difference between Spark and MapReduce is that Spark processes and retains data in memory for subsequent steps, whereas MapReduce processes data on disk.