A Canonical tag is an HTML tag that you can add to your website when you have two or more pages with duplicate content, and to standardize the official preferred URL when your site has multiple URLs. Let’s say that you have three different URLs that route to the same information. Google and other search engines do not like seeing the same information and content on different URLs because it looks spammy. By using a Canonical tag, you can choose one specific URL to route the information to. This will eliminate the redundant URLs. A Canonical tag is the simplest way to let Google and other search engines know that the content on your site is not duplicate, even though it looks like it.
Let me share with you a video from Matt Cutts (this guy is an amazing resource) about what a Canonical tag is and what Google wants every one to know about them.
Just like some of the other standards that Search Engines have agreed on, a Canonical tag needs to be used in the proper manner. It is used to prevent duplicate content from being indexed improperly on your site.
It sounds simple enough but again if you are like me, reminders help a lot to make it easier to understand. As always if you have questions feel free to comment or to call us. Thanks!