Your content is actually stored on server, and server have it’s own IP, but people can’t remember server IP like 184.108.40.206 .So later, computer scientist introduce DNS, so anyone can remember the name of server easily. For example google.com is easy to remember compare to above IP address.
So, IP canonicalization is same thing like normal canonicalization, for example, you serve same content from 220.127.116.11 also from google.com, so it is kind of duplicate issue, and that’s know as IP canonicalization, because your content is displayed thorough your domain name as well as from IP address.
But most of time, IP is automatically redirect to it’s domain name, so in 99% case, IP canonicalization is not happen. Normally, this type of problem is occurred in bulletin system(forum) like mybb, simplemachine, vBulletin etc.
You did not worry about it, if you are using blogger, wordpress, tumblr etc.
Advantages is, you can prevent duplicate issue, but As I said, only 1% people serve content from both IP address and domain name, all other system is automatically redirect to it’s custom domain. So there is nothing about advantages or disadvantages.