By now you have heard about the Heartbleed Bug affecting many sites. It has to do with vulnerabilities in the encryption in OpenSSL used by many sites for security.
How does that pertain to you, the end user? Well, you may need to change a bunch of passwords. Many sites were left vulnerable and it is suggested you change your passwords. How do you know if you have to do this? There are a few Heartbleed checkers out there that allow you to put in the url of the site you are concerned about. This will let you know if they were/are vulnerable to the bug.