ARP is Address Resolution Protocol. Check out http://www.watchguard.com/glossary/a.asp
for an overview or http://www.erg.abdn.ac.uk/users/gorr...pages/arp.html
if you want real detailed stuff. If you are using DHCP (from a router) you want it enabled, if not you might get away with disabling it. Depends what what s/w you use and what for.
Best thing to do is try it.