In Salesforce Marketing Cloud Engagement, items such as email templates, content blocks, and data extensions can be made accessible to users across different business units by storing them in a shared folder. Shared folders are designed to facilitate collaboration and reuse of assets within an organization's Marketing Cloud instance, allowing users from any business unit to access and utilize shared items in their campaigns and workflows.

By organizing and storing reusable assets in shared folders, businesses can ensure consistency in branding and messaging across different teams and campaigns, while also improving efficiency by reducing the need to duplicate assets for each business unit.

References: Salesforce Marketing Cloud documentation on content management and organization provides guidelines on how to use shared folders to manage and share assets across business units, highlighting best practices for organizing and accessing shared content within the platform.