What is Spam?
Spam is unsolicited advertisements that usually come in the form of emails. Some email providers come with spam filters that will recognize these email and send them to your junk folder. Certain words in the subject or the body of the email can set off your spam filter. To avoid legitimate emails from going into your junk folder or you trash, you can add the sender of the email to your contacts and this should prevent their emails from getting filtered.
Spam can be confused with website ads. Online ads are not considered spam. When visiting a website you are voluntarily viewing their webpage and the website owner has the right to display ads. This is usually done as a way to generate income.