This article explains what an ATN file is and how you can use it on your computer.

A file with the ATN file extension is an Adobe Photoshop Actions file. It records steps/actions in Photoshop and is intended to be "played back" later to automate the same steps.

ATN files are essentially shortcuts through Photoshop that are useful if you find yourself going through the same steps over and over again. These steps are recorded so that Photoshop knows exactly what to do when you execute the action file.

An ATN file can be used on any computer that opens it, assuming the same executables are present in the Photoshop installation.