What is a layer?

Layers are the mechanism used to display geographic datasets in the ArcGIS suite of products. Each layer references a dataset—which can be a map service, graphics, or vector data—and specifies how that dataset is portrayed using a set of properties.

Each application containing a map control is assembled by adding a series of layers. Layers are displayed in a particular order displayed in the map's table of contents. Layers listed at the bottom are displayed first, followed by the layers above them.

Layers are assembled into a collection and viewed in the map. Layers are displayed in a bottom to top order. As layers are rendered, subsequent layers are rendered on top of previous layers.

A list of layer types and descriptions is as follows:

• Graphic layer—Displays graphics.

• Dynamic map service layer—Displays non-cached tiled map service data as well as local map package data.

• Tiled layer—Displays cached map service data that requires a uniform resource locator (URL) to a map server.

• Tiled cache layer—Displays local tile cached data that requires a local path name to tile cache data.

• Feature layer—Displays points, lines and polygons. Used to display pop-up windows or to edit the data.