Slugs and query parameters are two ways to put information into a URL. A slug is a readable path segment like /blog/email-deliverability. A query parameter is a key-value pair after a question mark like ?id=42&sort=asc. They suit different jobs.
The distinction matters for SEO and usability. Slugs describe stable, unique content and read cleanly; query parameters carry variable state like filters, sorting, or tracking. Using the wrong one creates duplicate-content headaches or ugly, unshareable URLs.
