A portion of a URL that passes additional data to a landing page. For example: ?p_id=42
The format for query strings is a name=value pair. The first query string in URL must be preceded by the ? (question mark) character. Subsequent query strings must be preceded by the & (ampersand) character.
Query strings are often called parameters because they are used to pass parameters to code that runs on a landing page.
Learn more about passing parameters to keyword landing pages from keyword landing page URLs in Search Ads 360.