Droplets are small, independent, applications that automate common tasks. You can save your current settings into such a droplet application and every time you drag some files on the droplet the files are automatically renamed according to these settings.
This feature allows you to automate frequent tasks such converting file names for upload to Windows systems, creating numbered file lists, etc.
All you need to do in order to apply the settings is to drag the new files onto the droplet icon.
Please note that while droplets have been a part of A Better Finder Rename for a long time, in recent years, more and more users have experienced problems with them. As macOS focuses ever more on security, creating and running independent mini-applications goes against the grain of what the operating system is trying to achieve and every time the security mechanisms become more sophisticated, they also become more error-prone and unfortunately introduce new bugs.
For this reason, we recommend using A Better Finder Rename 12’s Presets feature to automate your renaming tasks as this new mechanism fits in much better into the new macOS eco-system.