A note is a non-Unified Modeling Language (UML) diagram element that contains textual information. A note attachment connects a note to another diagram element.
You can add a note to a diagram to provide comments, observations, or explanations about a particular diagram element. If appropriate, you can also attach a single note to multiple diagram elements.
As the following figure illustrates, a note is displayed as a rectangle with a folded upper-right corner, and a note attachment is displayed as a dashed line that connects the note to the diagram element.