What is "Sitecore Unicorn" primarily used for?

Sitecore Unicorn is primarily used as a serialization tool for managing Sitecore items. It enables developers to serialize Sitecore items, which means converting them into a format that can be stored in version control systems, such as Git. Serialization is crucial for tracking changes made to items within the Sitecore content tree, facilitating collaboration among team members, and ensuring that the Sitecore database state can be accurately replicated or restored.

Unicorn allows for automatic updates and management of serialized items, simplifying the deployment process and making it easier to maintain different environments (like development, staging, and production). By using Unicorn, developers can work more efficiently on Sitecore projects without losing track of content changes or configurations across various environments.

The other options highlight different tools and services that relate to Sitecore but do not define Unicorn's primary function. For instance, while analytics is critical for monitoring user interaction with the site, a content delivery network focuses on speeding up content delivery, and design tools assist in the layout aspect of website development, none of these capabilities pertain to the serialization functionality that Unicorn provides.