A Phishing e-mail is an e-mail that purports to be something it is not. Phishing e-mails are sent from scam artists who are trying to get you to give them your personal information. Phishing is a very serious crime, because it results in identity theft and stealing in general. It is important to report phishing both to the government's site for anti-phishing and to the company that has been phished.
Make a copy of the e-mail and include all of the information. You can take a screenshot if you would like. Make note of the e-mail address that the e-mail was sent from. If the e-mail leads you to a link, copy the address of that link and take a screenshot of the website.
Forward the phishing e-mail, or send all of the information you have collected, to email@example.com. Workers will look through your information and try to find the culprit.
Go to the website of the company that the e-mail pretended to be. It might be a bank, a business, a cell phone company, or a company that handles money like Western Union or PayPal. Look at their website to see if they have a "Report Phishing" link. Most companies do, especially those that are prone to phishing. If they have one, send them an e-mail with the information about phishing as well.