Session cookies are small pieces of data stored by your web browser while you are actively using a website. They help websites remember your login status and preferences during a single browsing session, making navigation smoother and more secure. Once you close your browser, session cookies are typically deleted automatically. However, if these cookies are intercepted or stolen by attackers, they can be used to impersonate you and gain unauthorized access to your accounts. This makes the secure handling of session cookies crucial for online safety.