Dictionary
Query string
The part of a URL after a question mark, carrying key-value data like a search term or a tracking reference.
In more detail
What It Means
A query string is everything in a URL after the question mark, structured as key-value pairs. It's commonly used for search terms, pagination, and tracking references, and unlike the path, it doesn't necessarily point to a different page, just a different state of the same one.
See it in context on the homepage: Anatomy of a URL.