What is Speculative Execution

Question

I'm exploring Hadoop on my own and came across a term speculative execution.
Can anyone explain what it is?

Answer 1

If a node is executing a task slower then the master node. Then there is needs to redundantly execute one more instance of the same task on another node. So the task finishes first will be accepted and the other one likely to be killed. This process is known as “speculative execution.”
Hope this helps.