These functions exist within a pflow.js file on your local computer as well as on the Landmark server.
This makes sense if you create a function that you might want to use over in your current flow or within a different flow later on. You can, however, create a function that will only be used once.
You will notice that you don't have to declare it to be a function, since it is assumed to be one when you build it. You will also notice that you can utilize the existing functions within this one.