You should define a canonical URL to be used on either similar or duplicate pages.
A canonical URL is the URL of the page that Google thinks is most representative from a set of duplicate pages on your site
So why should you set up a canonical URL? There are a number of reasons:
- To manage syndicated content that you may have been published on another domain
- To stop the Googlebot crawling duplicate pages, and therefore wasting your crawl budget
- To determine the actual URL you wish to appear in search results
- The consolidate the link signals to similar pages that come from other websites
- To make tracking metrics more simplistic
So as you can see, there are a variety of important reasons why the correct canonical URL setting should be in place.