A Note element is a textual annotation that can be attached to a set of elements of any other type. The attachment is created separately, using a Notelink connector. Both Note and Notelink are available in any Enterprise Architect diagram, through the 'Common' pages of the Toolbox.
A Note is also called a Comment.
Note elements do not have a Properties dialog. You can give them a name in the Properties window, but this does not display on the diagram.
You can configure Enterprise Architect to display the text in all Notes elements in italics. Select the 'Start > Appearance > Preferences > Preferences' ribbon option and on the 'Diagram > Appearance' page select the 'Italic Note Element text' checkbox. This has an immediate effect, as does clearing the checkbox to show the text in normal font.
OMG UML Specification:
The OMG Unified Modeling Language specification, (v2.5.1, p.40) states:
A Comment is a textual annotation that can be attached to a set of Elements.