It means that you have some url parameter loading from site, as reaction to some plugins, or file, or some changes, or behavior on site that may be loaded by some php code. In this scenario it can’t be exactly seen where is it coming from, but it looks like starting some type of increment.
But most important you can’t just change the url site with added paramete ?i=0 that is not the way this functions, and you can’t change your adress to something like this.
If you need to transfer your site from domainexample1.com to domainexample2.com/?i=0 you shouldn’t worry about this ?i=0 because if you are going to delete all content from domain2 and put there domain1 content it will not happened as this ?i=0 part is result of some functionality on this site.
