If you do anything online, you have probably heard of the term 'phishing'. Phishing is a type of scam whereby the scammer sends e-mails, posing as a real organization, in an effort to try and capture your personal information. The e-mails are typically made to look official, and sometimes it's hard to tell whether the e-mail is real or fake. Often, the tone of a phishing e-mail will be urgent, and will request you click on their link right away or your account will be frozen, or some such bad result. Phishing e-mails can be made to look like they come from your bank, internet provider, eBay, etc.
The IRS has a good page about phishing, where they describe what it is, examples of what it might look like, and what to do if you receive such an e-mail. Click here to go to their site and read the fully story.