Magento 2 Canonical URL extension helps you to add canonical meta tags for products, categories, CMS pages, home page, pagination, layered navigation, and any other pages of your site.
In Magento 2, the canonical URL is an HTML link element that tells search engines which is the preferred or canonical version of a webpage when multiple versions of the same content exist. It helps search engines understand the original source of the content and avoids duplicate content issues. Canonical URLs help in resolving duplicate content issues by specifying the preferred URL for a particular page.