[Streaming]What is the difference between streaming options: -file and -CacheFile ?

[Steve Gao]

Hi All,  
    I am using Hadoop Streaming. I am confused by streaming options: -file and 
-CacheFile. Seems that they mean the same thing, right?

    Another misleading options are : -NumReduceTasks and -jobconf 
mapred.reduce.tasks. Both are used to control (or give hit to) the number of 
reducers.

  Thanks