I think I am almost lost in the internals of Spark

[Todd]

I am a bit new to Spark, except that I tried simple things like word count, and 
the examples given in the spark sql programming guide.
Now, I am investigating the internals of Spark, but I think I am almost lost, 
because I could not grasp a whole picture what spark does when it executes the 
word count.
Is there detailed guide into the intervals about what spark does when it 
execute the word count?Thanks. There is a lot of good explanation about the 
process how Hadoop does the word count.