The Notes operator lets you add a textual comment to any event. It doesn't have any direct effect on the particle system, but it helps you keep track of the overall function of each event.
Note: You can also add a comment directly to an event or action by right-clicking it and choosing Comments.
Interface
The user interface appears in the parameters panel, on the right side of the Particle View dialog.
The interface is a simple text box. Click in the box and enter your text.