A ping of death (abbreviated "POD") is a type of attack on a computer that involves sending a malformed or otherwise malicious ping to a computer. A ping is normally 56 bytes in size (or 84 bytes when IP header is considered); historically, many computer systems could not handle a ping packet larger than the maximum IP packet size, which is 65,535 bytes. Sending a ping of this size could crash the target computer.
Traditionally, this bug has been relatively easy to exploit. Generally, sending a 65,536 byte ping packet is illegal according to networking protocol, but a packet of such a size can be sent if it is fragmented; when the target computer reassembles the packet, a buffer overflow can occur, which often causes a system crash.
This exploit has affected a wide variety of systems, including Unix, Linux, Mac, Windows, printers, and routers. However, most systems since 1997-1998 have been fixed, so this bug is mostly historical.
In recent years, a different kind of ping attack has become wide-spread - ping flooding simply floods the victim with so much ping traffic that normal traffic fails to reach the system (a basic denial-of-service attack).
It doesn't take a whole lot of looking into. Looking into a 10 year old attack isn't going to do you a whole lot of good.