I am just concerned because people downvote and for no reason, I don't understand this rule, should people downvote and take off running or should they give a reason for doing so? I'm confused.
Every downvote does have a reason even if it's not stated explicitly by the voter.
It's right there when you hover over the down arrow
This question does not show any research effort, is unclear or not useful.
If the voter feels it meets one of these conditions then no explanation is necessary.
I will grant that commment would be a nice addition but it's not, never has been and, based on many previous responses from moderators and SE employees, never will be mandatory.
The second the site requires comments for downvotes, is the second the site gets filled with comments that read:
stgouihj nwet gpojaygh-90i1248y 28iujtgoiwjrg0913 2glkjngopw
Because I have to
Blah blah blah blah
Forcing them to comment doesn't guarantee that you'll get a useful comment. It also invalidates the SE belief in private voting. If you're forced to comment when you downvote, everyone now knows that you've voted on the question.