Phishing is a technique that hackers use to get to your personal information. They pretend to be websites such as Amazon.com or Ebay.com. They send messages that say you need to update your password or other scams that you may click on.
After you click on it a malware gets installed and the hacker take whatever info they can find or mess up your computer. Usually when this happens, call that place and ask if the message you just got is genuine.