Query parameters within a URL typically represent the client's input or choices and can be points where SQL injection, Cross-Site Scripting (XSS), and other types of attacks might be possible. Such parameters are often appended after a question mark ('?') and can be manipulated to test for vulnerabilities in the processing of user input. It's crucial for penetration testers to identify and scrutinize these potential injection points. Hostnames, protocols, and path directories are generally static parts of the URL and, while important for reconnaissance, are not typically injection points.