Spam (or unsolicited e-mail) is mass correspondence sent to numerous recipients without their agreement or wish. The term spam appeared not so long ago (around 1993) but is already one of the most discussed matters in the world wide web. In spite of the fact that Internet is mostly regarded as unregulated information area there is still a number of limitations. Unfortunately they are not followed by everyone (only Internet old-timers) and spammers are the ones who commit the breach of Internet peace.
At present one has a very vague idea of spam. Usually an average Internet user considers spam to be an e-mail of advertising nature. However, spam is a rather wide notion that includes several categories. Generally spam is an unsolicited e-mail the user has not subscribed for. This may be either ads or important information the recipient has not asked for. Advertising in Internet is very cheap comparing to mass media sources. Spammers do not pay anything - providers and recipients are carrying the main load of unsolicited e-mails.
Ad is the earliest type of spam: it originated "the war against spam" by publishing unnecessary commercial information in Usenet news groups. In a narrower meaning spam is any useless information sent without recipient's agreement, even if it is vitally important for someone else.
Internet is also a great possibility to advertise the prohibited products (such as pornography). It is really hard to define the people responsible for such e-mails: companies sending such correspondence often act as mediators between the owner of information and the destination of it. That is also the reason of difficulties for legislation: some countries already passed laws against spam which are hardly applicable in case of boundary hindrance. Another type of spam is placing any type of off-topic information in different conferences (information that does not directly relate to their topics).
The types described above are relatively innocuous; however, there are others that are aimed at pulling out recipients' money. Unsolicited e-mails have brought troublesome fame to Nigeria. Not long ago Internet was flooded with so called "Nigerian letters" offering a recipient an easy scheme to get rich: one just had to send a ridiculous sum of money - and BINGO! A more sophisticated way of cheating is so called "fishing", when the objective is to get credit cards numbers and passwords. Such e-mails are written in the form of an official bank notification saying a recipient can solve emergency problems occurred to his or her account by filing in the form on the corresponding site (obviously belonging to spammers).
Therefore spam or unsolicited e-mail is any illegal e-mail not wanted by recipients. The content may differ from religious to official but its nature will stay the same, and the fight against it should result in the complete obliteration of it.