A Canadian Certificate of Identity is a special document that can help you travel outside of Canada if you are not able to get a passport. For example, if your passport is lost or stolen or if you cannot get a passport because of legal reasons, you can apply for a Certificate of Identity instead.
It looks kind of like a passport, with pages and a photo of you inside, but it's not exactly the same thing. The government of Canada makes sure that the information in the Certificate of Identity is correct, just like they do for passports.
If you need to travel outside of Canada and you can't get a passport, you can apply for a Certificate of Identity by filling out some special paperwork and sending it in to the government. They'll also need some other documents from you to prove who you are.
Once you have your Certificate of Identity, you can use it to travel to other countries. Just remember that not all countries will accept a Certificate of Identity in place of a passport, so be sure to check before you make any travel plans.