Hi Vamsi,
ARP poisoning is an attack that is accomplished using the technique of ARP spoofing.
ARP spoofing is a technique that allows an attacker to craft a "fake" ARP packet that looks like it came from a different source, or has a fake MAC address in it.
An attacker uses the process of ARP spoofing to "poison" a victim's ARP table, so that it contains incorrect or altered IP-to-MAC address mappings for various attacks, such as a man-in-the-middle attack.
Hope that helps.
-Mike
