Here are a few terms one should be aware of when using the Internet:

Viruses
A computer virus is a self-replicating computer program that spreads by inserting copies of itself into other executable code or documents. A computer virus behaves in a way similar to a biological virus, which spreads by inserting itself into living cells. Viruses are one of the several types of malicious software. The term virus is often extended to refer to worms, trojan horses and other sorts of malware. While viruses can be intentionally destructive, for example, by destroying data, many other viruses are merely annoying. Viruses are most commonly spread by email.

Spam
E-mail spam involves sending nearly identical messages to thousands (or millions) of recipients. Perpetrators of such spam ("spammers") often get addresses of prospective recipients from newsgroup postings or from web pages, obtain them from databases, or simply guess them by using common names and domains. To avoid being spammed you should always be protective about your email address.

Chain emails
A chain message, or chain e-mail, is defined as any message sent to one or more people that asks the recipient to forward it to multiple others and contains some promise of reward for forwarding it or threat of punishment for not doing so. Chain messages can cause "traffic congestion", slows down Internet traffic and offers spammers list of addresses.

Email hoaxes
An email hoax is an outrageous, ingenious, dramatic, sensational and deceptive email message.

Hackers
A slang term for a computer enthusiast, i.e., a person who enjoys learning programming languages and computer systems and can often be considered an expert on the subject(s). Among professional programmers, depending on how it is used, the term can be either complimentary or derogatory, although it is developing an increasingly derogatory connotation. The negative meaning of the word hacker is becoming more prominent largely because the press is using the term to refer to individuals who gain unauthorized access to computer systems for the purpose of stealing and corrupting data.