The role of cookies in a web browser is to store user information and settings while browsing the internet. Cookies help websites remember your preferences, such as login credentials and language settings, enhancing the overall user experience. They also track browsing behavior to personalize content and advertisements, which can improve engagement. However, this practice raises concerns about privacy and data security, prompting regulations like GDPR to ensure users have control over their personal information. Overall, cookies are essential for a smoother, more tailored online experience.