annotation
an·no·ta·tion
/ˌænəˈteıʃən/ noun , pl -tions
1 [ count ] : a note added to a text, book, drawing, etc., as a comment or explanation
Without the annotations, the diagram would be hard to understand.
2 [ noncount ] : the act of adding notes or comments to something : the act of annotating something
the author's annotation of the diagram
