A link/button destination can be:

In the context of OutSystems and web development in general, a link or button can serve multiple purposes based on its configuration. When considering the option that states both external and internal destinations are possible, it becomes clear why this answer is correct.

In web applications, links/buttons can be set to navigate to external URLs, directing users to other websites, or to internal pages within the same application, which enhances user experience by enabling easy navigation. This flexibility allows developers to create seamless transitions, guiding users to the necessary resources or sections of the application they need to access.

The other choices imply limitations that do not reflect the functional capabilities of OutSystems. The idea that links/buttons could only be external or only internal does not align with the reality of how navigation can be configured in a web application, which can involve both types of destinations based on the needs of the application and user experience design. Therefore, the ability to designate both internal and external links/buttons is a crucial feature for any web application development framework, including OutSystems.