The term Canonicalization is hard to pronounce, but it’s one of the most important terms in the world of SEO. It refers to how a website can use different URLs for the same piece of content (usually the entire web page). For example; every website resolve to a particular IP address of the hosting machine. It means, the website can be accessed via its domain name (http://example.com or http://www.example.com – you can fix this via 301 redirect) and at the same time it can be accessed using the IP address as well.
The canonicalization problem occurs, when a website’s IP address and domain name display the same page, but do not resolve to the same URL. This behavior is not search engine friendly, because the spiders are unsure as which URL is the correct one (If I put it right, which page is a Canonical one among the set of pages with same contents). The search engines doesn’t like duplicate contents and so the IP canonicalization is very important in SEO point of view.