According to Wikipedia, Phishing (also known as carding and spoofing) is the act of attempting to fraudulently acquire sensitive information, such as passwords and credit card details, by masquerading as a trustworthy person or business with a real need for such information in a seemingly official electronic notification or message.
The people who are phishing for information are mostly con artists, although there are some doing it merely because they can and think it's funny. What are they phishing for? Your personal financial access. They do these to access your bank account or credit account. When you click on their e-mail request to sign in, you are not taken to the site you think you are going, but a bogus site that looks exactly like the real one. When you log into your account, the phisher now has your log in information and can immediately go to the real site and log in then change all your information so you cannot get into your account, but they can. In the meantime, they have plenty of time to drain your account or run up credit charges or get enough information about you to commit identity fraud.
If you get an e-mail from any bank, credit card company, PayPal, eBay or any others that have such personal information listed on it, proceed with caution.
First check the headers of the e-mail. Does it actually lead back to the right company or is there another domain in the header that shouldn't be there?
Next, place your mouse over the link, but do not click on it. Is the main domain of the URL proper, or is it an alteration of the real domain. For instance, instead of Paypal.com it may read account-paypal.com or user.paypal.com. Unless the www. is followed directly by the proper domain name, it is probably a hoax.
How is it addressed? Unless it is addressed to you by your correct name when you signed up, it is probably bogus. Banks, credit card companies, even eBay and PayPal will address you Dear YOUR NAME and not a generalized greeting such as Dear Customer or To All Our Banking Customers.
What exactly is the request? If they are claiming for whatever reason security has been breeched or there was some flaw requiring you to log in, CALL THEM IN PERSON! Whenever you deal with banks or credit card companies, you should always have their emergency numbers written down somewhere. Call that number and confirm if it is a bogus or real warning.
If they are claiming they are going to delete your account due to inactivity, do you really care if you have really been inactive that they are going to delete your account? If a bank or credit card company were to delete your account, you would get a letter in the postal mail not by e-mail. If you are inactive with companies like PayPal or eBay, they do not just routinely delete inactive accounts, but will have you verify your current information when you do decide to log on again.
If you are unsure, do not click any link on the e-mail. Open up a browser and manually type in the web site address of the company and log into your account or find a place, if available, to talk to a person live. If you were able to access your account and nothing looks out of place, feel free to change your password if you wish and report the fraud e-mail or delete it.