Understanding Layers and Layer Controls
What Is A Layer?
A "Layer" is a set of information or data. For instance, one layer could be 'counties' in New York State. Another layer could be 'interstate highways' in New York. These layers are laid on top of each other and are visible as a single map image. Add more layers about cities, rivers or other information and you get a more detailed map displaying more information.
The Active Layer Dropdown Menu
The Active Layer menu is used to make layer details accessible for the Identify tool. The menu lists the data layers in the current view of the Navigator. These layers are also listed in the Map Layers list below the "Refresh" button. Each layer contains a specific type of data. From the Active Layer Dropdown Menu, you choose a layer, making that layer available for use with the Identify tool.You must activate a layer if you want to use the identify tool.
The Map Layers List
The Map Layers List is used to make more or less detail visible. It lists the data layers in the current view of the Navigator. Certain layers will only appear when you zoom in to a certain scale. Beside each layer name is a check box. Checking the box next to a layer will make that layer visible and unchecking it will make it invisible, but you must first click the "Refresh" button. You must click the "Refresh" button every time you change the visibility of a layer.
The Refresh Button
Each time you make a layer visible or invisible by checking or unchecking the checkbox next to it, you have to click the refresh button to update the map.