[m2e-users] What does Maven ->Download Source do?

[Steve Cohen <scohen@xxxxxxxxxxxxxxx>]

I invoke this option on a Jar listed under Maven Dependencies.  Most of 
the time, nothing happens.  No visible cues whatever that anything is 
occurring.  Once, I did see the Downloading Source status message, for 
several seconds, but it gave me no message, and the source was nowhere 
to be found in my local repository, nor did the class for which I wanted 
to view the source display that source.

How would I use this option?