Path variables are part of the URL that represent the data you are requesting or sending. They are typically used when the data is essential to the URL structure itself. Path variables are often used to specify a resource or entity. Query parameters are part of the URL but are separated from the base URL by a ?. They are typically used to filter or modify the request and are not considered part of the path itself. Query parameters are commonly used for optional inputs like filters, pagination, or search queries.