Phishing is an email fraud method in which the perpetrator sends legitimate-looking email in an attempt to gather personal and financial information from recipients
Spoofing refers to email that appears to have been sent from someone other than the real sender. Virus writers and individuals who send junk email or "spam", typically want the email to appear to be from an email address that is not their own. Thus, the email cannot be traced back to the originator.
Spam is any email message irrespective of content that is unwanted or unrequested by the recipient.