A canonical page is the preferred version of a set of pages with highly similar content.
It's common for a site to have several pages listing the same set of information. For example, one page might display products sorted in alphabetical order, while other pages display the same products listed by price or by rating.
Search engines now support a format that allows us to publicly specify your preferred version of a URL, providing us with more control over the URL returned in search results. Search Engines will understand that the duplicates all refer to the canonical URL.
Adding a canonical link and attribute lets site owners identify sets of identical content and suggest to Search Engines: "Of all these pages with identical content, this page is the most useful. Please prioritize it in search results." It also helps to make sure that properties such as link popularity, PageRank and related signals are consolidated to your preferred version.