Presumably, that's just the name of a field. Since you can name a field almost anyway you want. It could be almost anything.
In the Contact Management template for example, those fields are used to display little triangles to indicate the current sort order. A global container field holds the graphic, and a calculated container field determines which graphic to display.
This technique has also been commonly used to indicate a selected record in a portal or list, although now we have other options (conditional formatting and/or script triggers).