1. Put plainly, spam is junk mail that is sent via email. It is a bad thing. The
Anti-Spam Home Page describes it this way:
A "spam" e-mail is generally defined as an unsolicited mailing, usually to many people. A message written for, and mailed to, one individual that is known to the sender is not spam, and a reply to an e-mail is not spam, unless the "reply" repeats endlessly.
Spam e-mailers have become a separate part of the Internet, with their own host computers, methods, and politics. Many Internet sites have begun to forbid spamming, for several reasons – one is a sense that it is unethical, another is that, over time, other Internet sites will stop all e-mail from that site and thus prevent legitimate e-mail from getting through. As a result, spammers have begun to set up their own Internet sites -- sites that cater to, or encourage, spamming.
2. A type of canned meat (or at least that's the general concensus) that was once used for k-rations. Some people love it, but some people "don't like spam".