URL parameters are extra pieces of information added to the end of a URL, usually after a question mark, that help a website change or track what a page displays. For example, ?sort=price might reorder products, ?color=blue might filter results, and ?utm_source=newsletter might track marketing campaigns. Parameters are common on ecommerce sites, search and filter pages, and analytics tagged links.
From an SEO perspective, parameters can create multiple URLs that show the same or very similar content, which can lead to duplicate pages and diluted ranking signals. To keep things clear, decide which version of a page should be the primary one and support that with canonical tags, consistent internal linking, and sensible rules for how parameters are handled. It also helps to avoid indexing low value parameter combinations, especially endless filter and sort variations that do not provide unique content. When parameters are managed well, search engines can focus on the URLs that represent your best, most accurate pages.