If you have two articles which is speaks about same thing then you can set canonical url to make that as original article.
For example: consider 2 articles:
By writing two article for the cat, surely the two articles will rank for the keyword "cat" It will create a duplicate content issue. In order to avoid it.
For 2nd article abc.com/ cat-tips in this article you are inserting canonical url abc.com/cat- foods. Which says google to pass all authority to abc.com/cat-foods. So this post will rank alone for the keyword "cat".
The rel=canonical element, often called the “canonical link”, is an HTML element that helps webmasters prevent duplicate content issues. It does this by specifying the “canonical URL”, the “preferred” version of a web page. Using it well improves a site's SEO.
Canonical URL means it is a important URL type of the website. Canonicalization URL signifies the preferred URL of altered versions of the related pages which may be caused by copied content issues. Essentially, it helps us to avoid copied content issues.