What is the primary function of a cookie on a website?

Cookies primarily serve the function of tracking the activity of a user on a website. When a user visits a site, cookies are small pieces of data that are stored on the user's device. They allow the website to remember information about the user's preferences, login status, and browsing history as they navigate through the site. This tracking capability supports features like personalized content, targeted advertising, and retaining items in a shopping cart.

While cookies can interact with aspects of security and performance, their significant role revolves around maintaining a connection to individual users and their behaviors during their visit, which can enhance the overall user experience. For example, when cookies are used, a website can tailor its interface according to the user's past interactions, making it more relevant and engaging.

The other options may seem appealing, but they do not align with the core purpose of what cookies do. Storing user passwords securely is typically managed through encryption and secure authentication mechanisms, not cookies. Improving webpage loading speed is influenced by various factors including server performance and caching strategies, not directly by cookies. Finally, while cookies can be part of a broader security framework, they do not primarily function to provide website security as their main objective.