What is a tiled layer?

ArcGIS for Server provides a map cache service, which is a regular map service that has been enhanced to serve maps very quickly using a cache of static images. The map cache is a directory that contains image tiles of a map extent at specific scale levels. ArcGIS Runtime applications can use a map service to access this tile cache through virtual directories. A complete cached map service uses the following components to do its work:

• Cache—Composed of a map service cache directory that contains a hierarchical collection of cached tiles (images) and a file (conf.xml) that contains a description of the cache called a tiling scheme.
• Web server—Hosts the actual map service, a web virtual cache directory referencing the actual cache directory, and a tile handler service used when the virtual cache directory is not directly accessible.
• ArcGIS for Server—Hosts map service instances that provide information about the map cache, serve query and data operations, and in some cases, provide map tiles when the cache is unavailable.

Tile package

A tiled layer is also the target layer for local tile package (.tpk) files. With the path to a local tile package, you can create a local tiled layer, which is a kind of tiled layer where instead of the tiles being stored online, as is the case for a tiled layer from a map service, they are all available locally on your machine. Tile packages are thus ideal in a disconnected environment or when network connectivity is limited, and are also great for sharing cached maps between colleages in a work group, across departments in an organization, or with any other ArcGIS user with ArcGIS Online. For more information on tile packages, please see About tile packages.