The buttons on the Symbols Pages labeled "Picture/text" are links to photos and text discussions of the associated symbols. Many of the photos are annotated to illustrate some feature of the symbol.
This particular photo is used here to illustrate tide heights. Elsewhere it might be used to illustrate lights or how cliffs are presented on charts, or what a "dolphin" is. There are many photographs in the program and generally several examples of each subject are presented.
From the photograph window, you can go directly to the index of other photographs, or open the text window associated with this picture.