Spam is basically junk mail or bulk mail, and it has serious affects on the internet. 

Spam wastes staff time. Users without anti-spam protection have to check which Spam is unsolicited commercial email, the electronic equivalent of the email is spam and then delete it.
junk mail that comes through your letterbox. Users can easily overlook or delete important email, confusing it with spam.

Spam, like hoaxes or email viruses, uses bandwidth and fills up databases. Some spam offends users. Employers may be held responsible, as they are expected prescription drugs, drugs that enlarge or enhance body parts, herbal remedies, or to provide a safe working environment.

Common spam messages are about weight-loss drugs, get-rich-quick schemes, financial services, e.g. mortgage offers or schemes for reducing debts, qualifications, e.g. university degrees, or professional titles available for purchase, online gambling, cut-price or pirated software, etc.

Spammers often use other people’s computers to send spam. Spam sometimes comes in disguise, with a subject line that reads like a personal message, e.g. “Sorry about yesterday”, a business message, e.g. “Your account renewal now due”, or a non-delivery message. Spammers often disguise their email in an attempt to evade anti-spam software.

People send spam because it is profitable. Spammers can send millions of emails in a single campaign at a negligible cost (and if they can hijack other people’s computers to send the mail, the cost is even less). If even one recipient out of ten thousand makes a purchase, the spammer can turn a profit.