When you process files with Spotless, the files are processed by a Task. A Task is simple a set of rules to decide which files Spotless should act upon, and what action to take for each. These rules can be very simple, or quite complex to give you the control you need. For example, you may create a rule in a task to move any files with extension JPG to the pictures folder, another to move any files with extension TXT to the Documents folder, and another to move all files with extension XLS which contain the word "accounts" in the filename and have a modified date newer than the 1st January 2018 to a subfolder of the Documents folder labelled "Current Accounts".
You can create as many Tasks as you like to define what should happen to files. For example you may wish to create one Task called "Organise Images" to tidy any images found into subfolders of the Pictures folder, and another called "Delete Old Files" which moves any files with a modified date older than a certain date to the trash. Tasks can have as many rules as you like, so you could have a single task which knows how to treat or your files, or create Tasks for individual jobs depending on what suits you.
As well as defining rules which determine if each file should be processed, a Task can also be configured to have a default action to perform on any files that do not match any of the rules. In this way you can tell a Task for example to move all files that weren't handled by the rules into the Spotless folder, so they are out of the way but not lost.
You can configure which Task is run when you perform a Drag & Drop onto the Spotless drop target, and can create Automation jobs to run a specific task at regular intervals. You can also configure each of these features to ask you which task you would like to run when they are processing files.