According to Apache, Spark is a fast and general engine for large-scale data processing. This is actually a really good summary of what it's all about. If you have a really massive dataset that can represent anything - weblogs, genomics data, you name it - Spark can slice and dice that data up. It can distribute the processing among a huge cluster of computers, taking a data analysis problem that's just too big to run on one machine and divide and conquer it by splitting it up among multiple machines.
The way that Spark scales data analysis problems is, it runs on top of a cluster manager, so your actual Spark scripts are just everyday scripts written in Python, Java, or Scala; they behave just like any other script. Your "driver program" is what we call it, and it will run on your desktop or on one master node of your cluster. However, under the hood, when you run it, Spark knows how to take the work and actually farm it out to different computers on your...