What is a key function of cookies in web applications?

Cookies serve a crucial role in web applications by enabling the storage of user preferences and session information. When users interact with a website, cookies allow the application to remember details such as login status, language settings, and other personal preferences that enhance user experience during subsequent visits. This ability to retain information is essential for personalizing interactions and providing a seamless navigation experience.

The other options do not align with the primary purpose of cookies. For instance, while data backup is essential, cookies are not designed for storing large amounts of data; they typically hold small amounts of information. Managing server-side logic is also outside the scope of what cookies do, as they primarily operate on the client side to affect the user experience rather than the underlying application logic. Lastly, enhancing website graphics quality is unrelated to the function of cookies, as graphic quality is managed through design and coding practices rather than the use of cookies. Therefore, the primary function of cookies in web applications revolves around remembering user preferences and session data.