Which script type is designed to execute actions based on a defined schedule?

Scheduled scripts are specifically designed to execute actions based on a defined schedule within NetSuite. They allow administrators and developers to automate processes or perform routine tasks at designated times, which can enhance efficiency and ensure that important operations happen consistently without manual intervention.

Scheduled scripts can be used for a variety of tasks, such as data clean-up, report generation, or sending reminders, and they run on the servers, making them ideal for background processing. The scheduling can be configured to run at specific intervals, whether that be hourly, daily, weekly, or at a specific time.

In contrast, user event scripts are triggered by specific events related to record interactions, like creating, editing, or deleting records. Mass update scripts are used to apply changes to multiple records based on criteria but do not run on a predefined schedule. RESTlet scripts facilitate communication with external systems, allowing for server-side code to be executed in response to HTTP requests, without being tied to a specific schedule.

Overall, the unique characteristic of scheduled scripts to operate automatically according to a preset time frame is what distinguishes them as the correct answer in this context.