Canonical Link Element
Defining The Authoritative URL
Canonical Link Element code clarifies the precise formulation of the correct URL. For most websites, typing any of:
will display the home page. However, these are all different URLs (Universal Resource Locator - or, in simple terms, web address), and search engines may treat them as different URLs or choose a version that you don't prefer. Canoncialization simply involves picking the URL you want, and telling search engines that this is your preferred URL.
If you do not specify which URL is your Canonical URL, you may be dividing your Page Rank among multiple versions of your page and hurting your search results.