When you first set up Site Kit, you will be prompted to set up Search Console so that you can see how your site appears in Search, how many impressions and clicks you got from Search, and how people found your content from Search.
Creating a new property
If your site does not already have an associated Search Console property, Site Kit will create a URL-prefix property and connect it to your site. URL-prefix properties only include URLs with a specific prefix, including the http/https protocol. See this guide for more details on URL-prefix properties.
Connecting an existing property
If your site does have an associated Search Console property before you set up Site Kit, Site Kit will automatically select that property to connect.
URL-prefix property
If you’ve already created a verified URL-prefix property for your site, it will be automatically connected during the Site Kit setup process.
Domain property
If you’ve already created a verified Domain property for your site, it will be automatically connected during the Site Kit setup process if the site URL is at the root level (i.e. https://example.com instead of https://example.com/blog). It will not be connected if you also have a URL-prefix property that has been manually verified, as that will take precedence and be connected via Site Kit instead. See this guide from Google for more details on Domain properties.