What does the “spam” selection do in the Moderation Panel

I am not clear and could not find a reference to the action taken by the “spam” selection or the “mark all as spam” selection on the Moderation Queue control panel.

What is different than just pusing “Delete this comment”?

I am starting to get some annoying messages in my comment queue so I thought this might help.

Sorry to bother you with what is just an operational question. If you point me to some documentation location I will read that there but the search did come up with anything useful.

Thanks in advance for your help.

Keep up the great work this is a wonderfully designed piece of software.

Bernie