"Email spam," "Junk email" or "Spam mail", usually referred to as just "Spam", are unwanted, unsolicited, commercial email messages, normally sent in bulk to a large distribution list of recipients.
Many spam emails contain URLs to websites and can be annoying as well as potentially risky because they can contain bogus offers that can cost you time and/or money.
In Office 365, your spam messages are placed in quarantine. You have the ability to review and release messages from quarantine into your inbox.