The file extension AET is used by the video compositing and animation software After Effects for template projects (templates). These contain settings for a project, such as image format or a set menu structure for a DVD. Templates serve as a starting point for your own projects with customized settings.
When an AET file is opened, After Effects automatically creates a new, untitled, template-based project. If the project is saved, an aep project file is generated. The template file remains untouched.