Hi Alex
These are parameters that sit after the main URL and often include 'sort' 'page'. (They can also be created in some eCommerce pages as 'products' but these should be dealt with a mod-rewrite to show properly constructed URLs with category name and title). There are a number of ways with dealing with them:
1. Google search console - you have to be very careful messing with the rules in parameter handling but for some, this is the way.
- 'sort' then you can tell Google that it narrows the content on the page - you can then choose to let Googlebot decide or block the URLs - I often block them as they just create skinny and duplicate content.
- Pagination - 'page' you can tell Google that this paginates and then let Google decide. Look at rel/prev tag on those pages as well.
- Attributes - like size and colour - I generally block those as they just create skinny duplicates of main categories
- Others - like Catalog - it depends on what platform you use but there could be other parameters being created - I block most of them as they create useless URLs
2. Robots.txt
You can use this file to block the indexing of these pages depending on the parameter by excluding them from being followed by the search bots. Once again be very careful as you don't want to accidentally block indexing of useful areas the site.
https://moz.com/learn/seo/robotstxt
3. Canonicals
If you are able a great way of dealing with attributes like size and colour is to canonicalize back to the non size specific URL - this is a great way of maintaining the link juice for those URLs which may otherwise be lost if you blocked them all together. You add a rel=canonical tag pointing to the non-parameter version.
https://moz.com/learn/seo/canonicalization
4. As a last resort you can 301 redirect them but frankly, if you have dealt with them properly you shouldn't have to. It's also bad practice to have live 301 redirects in the internal structure of a website. Best to use the correct URL.
There is more reading here:
https://moz.com/community/q/which-is-the-best-way-to-handle-query-parameters
https://moz.com/community/q/do-parameters-in-a-url-make-a-difference-from-an-seo-point-of-view
https://moz.com/community/q/how-do-i-deindex-url-parameters
Regards
Nigel