In this context, ferrous means iron, or an alloy
containing iron.
Examples: cast iron, carbon steel, stainless steel
non-ferrous just means a pure metal or alloy that
doesn't contain iron.
Examples: brass, lead, aluminum, titanium, beryllium-copper.
When a steel wrench is dropped on a concrete floor, it can create a spark. This can be a problem if you're working near flammable vapors, or in a combustible atmosphere. Because of this concern, OSHA requires the use of non-sparking tools in hazardous environments.
Non-ferrous alloys can be used to make
non-sparking tools. This means that they wont generate spark from impact or friction (like a dragging car tailpipe does).
This doesn't mean that non-sparking tools made from non-ferrous metal won't conduct an electric spark; this may be a point of confusion.
Both types of metal conduct electricity.
The anti-static mat is a good idea when you may have loose powder, primers, or priming compound on the bench; other than that, I didn't find amamnn's post to be very informative. There is some more discussion of static electricity in this thread:
http://www.thefiringline.com/forums/...d.php?t=391093