Which type of scripts run in the browser?
UI policies dynamically change the behavior of information on a form and control custom process flows for tasks.
For example, you can use UI policies to make the number field on a form read-only, make the short description field mandatory, and hide other fields
Note: Script Include, Access Control Scripts, and Business Rules run on the server-side
https://www.servicenow.com/docs/bundle/washingtondc-platform-administration/page/administer/form-administration/task/t_CreateAUIPolicy.html