it is unwanted sent to your email account or by SMS to your phone. these normally get rich quick schemes, advertisements.
Spam or junk.
No. Viruses can often come with junk mail, but the junk mail as such doesn't do anything apart taking up inbox space. If you simply delete it nothing bad happens. But if you run a virus it will try to do some damage. Maybe steal your credit card information, maybe hijack your email address and send further junk mail to others. Maybe...
If you sign up for certain websites and they ask for your email, and you give it them they will sometimes pass it on to other websites and they send you spam and junk mail.
spam
SPAM
This question.
Spam.
Most email programs, such as Microsoft Outlook, have options that allow you to set junk mail rules. These allow you to define senders, subject lines, and email body content patterns that will be used to filter emails into your junk email folder, or automatically delete them, rather than being sent to your Inbox.
Look up junk mail filters, or just switch to gmail, there is a powerful junk filter included.
Email junk mail-annoying Junk mail that you receive in your mailbox- waste of paper, waste of shipping
To get off junk mailing lists, you should consider a preferential mail system and service. Alternatively, if the mail is junk email, you should email the companies and ask your name to be removed.