The mural is the long narrow window at the right of the document. When you are viewing or editing a document which has comments in it the mural will show a reference to each comment within the document. Each comment reference within the mural has the same color as the corresponding comment in the document. Also, the position of the comment reference within the mural is the same as the position of the comment in the document. If you click on one of the comment references within the mural the document will be positioned so that the comment you chose will be at the top of the document window.