Dynamic URL
A dynamic URL is a web address built on the fly from parameters, usually after a question mark, like ?colour=oak&sort=price.
A dynamic URL is a web address that's put together on the fly, usually from a database query, with parameters after a question mark. harrowandpine.com/tables?wood=oak&sort=price is dynamic. harrowandpine.com/tables/oak is static, or at least looks it.
Dynamic URLs are normal on shops, search pages and anything with filters. They only become a problem when they multiply, because every combination of parameters looks like a separate page to a crawler.
Where the trouble starts
Filters and sort orders are the usual cause. Three woods, four sizes, five colours and three sort orders already make 180 addresses for one list. Add tracking codes and session IDs and the number keeps growing.
Search engines can spend their visits crawling all those near-identical pages instead of the ones you care about. Links and shares get split across the versions. Google's advice on URL structure is to trim parameters that don't change the content, avoid session IDs in addresses, and keep the variations crawlers can reach under control.
How to keep them tidy
You don't have to get rid of dynamic URLs. Give the pages that matter a clean, readable address. Put a canonical tag on filtered and sorted versions that points to the main list. Keep tracking codes out of internal links. If a set of filter combinations has no value in search, keep crawlers out of them.
For example, Harrow & Pine's oak table list is reachable at dozens of addresses through its filters. It gives the list a clean address, /tables/oak, links to that everywhere, and points the filtered versions at it with a canonical tag.
Dynamic URLs and AI answers
AI answers cite pages by address, and a citation is easier to read when the address says what the page is. When one page is cited under several dynamic addresses, its citations are split, and it's harder to see how often the platforms really use it. Clean addresses also help AI platforms' crawlers spend their visits on pages worth reading.
In AnswerOrbit
Sources lists every page the answers used, by its full address. If one of your pages shows up several times with different parameters, it's a sign it needs a canonical tag. See Sources.