They just had to find the desired location, mark it, and submit their request. After that, every time the two platforms received a new satellite image of those locations, users were notified.
The service launched in 2011, and at the time, it was the only tool users could use to follow what new images Google had added to their platform.
Later, however, Google Earth started to add 3D coverage to listed areas, and after that, 2D satellite images. There was also the Google Earth Medium account that provided regular updates on new content.
All that led to Google’s decision to shut down the service in 2019. Existing users had until the end of September to save their data. After that, Google deleted the tool.