Every map has a table of contents. The table of contents shows you what layers the map contains and how the map symbolizes the geographic features in those layers. Map authors can control whether the table of contents is displayed in ArcReader.
Some maps with two-dimensional content display all the layers in one data frame. Others, such as those with insets and overviews, have more than one data frame. The table of contents shows how the layers are organized into data frames. When viewing a map, you'll use the table of contents primarily to turn layers on and off.
Maps with 3D globe content display all the layers draped on the globe. Layers on a globe can have elevation offsets and may not display in the table of contents order. Since globes do not have data frames, map authors may create group layers to organize layers in the table of contents.