What is the purpose of domains in Sitecore security?

The purpose of domains in Sitecore security is to group users and roles, which allows for effective segregation of security contexts. This organization is crucial because it enables Sitecore administrators to define specific security policies and permissions for different groups of users based on their domain. By using domains, organizations can streamline the management of users and roles, ensuring that each user has access only to the information and functionalities relevant to their job responsibilities. This adds a significant layer of security and control over the content and features that users can access within Sitecore.

Other options do not align with the primary function of domains. Content personalization is a feature that can be enhanced in other ways, and managing content languages or Sitecore licenses pertains to different organizational needs that are unrelated to the security structure defined by domains. Therefore, the focus on grouping users and roles is a foundational aspect of how security is structured in Sitecore, which makes it the correct choice.