Make notes, or more likely set variables for future use. These are all the properties of Note and what they do:
A label that you can use to easily identify this step.
A text field where you can type anything you like. It will not be rendered on your components.
Allows you to turn off this step programatically. If this field has any contents, then it will be processed by the template engine. If after processing the field has any value other than empty or 0, It will render. If it is empty or 0, it will not render, much the same as if you had disabled it.
Besides taking notes, the most common use for this step is to set variables using template functions.