An ArcGIS web map is an interactive display of geographic information that you can use to tell stories and answer questions. For example, you may find or create a map that addresses the question, How many people in the United States live within a reasonable walk or drive to a supermarket? This map has layers showing which neighborhoods are within a 10-minute drive or 1-mile walk to a supermarket, and for context, the map has a topographic basemap that includes cities, roads, and buildings overlaid on land cover and shaded relief imagery.
Maps contain a basemap, a set of data layers (many of which include interactive pop-up windows with information about the data), an extent, and navigation tools to pan and zoom. In general, the basemap and layers are hosted and shared through ArcGIS Online. However, maps can also contain layers added directly to the map and layers and basemaps referenced externally. Many maps also contain scaled symbols and other smart styling that reveal data and patterns as you interact with it. For example, the map below shows the relative magnitude of earthquakes that happened over the previous 60 days.
The map has several zoom levels, each level revealing more detail the closer you get. Click on any earthquake symbol to learn the magnitude and date of each event. The map also has scaled symbols, showing the relative magnitude of each earthquake. The background map is symbolized as well in muted dark tones that set off the bright earthquake symbols. This data, organized with this combination of symbology, reveals a pattern of earthquakes known as the Ring of Fire.
Maps can be created in a few basic steps and opened in standard web browsers, mobile devices, and desktop map viewers. They can be shared through links, embedded in websites, and used to create map-based web apps. When a map is shared, the author decides what to include with the map. For example, when the map is shared to the general public through Map Viewer, the map includes options to switch basemaps; view a legend (if the map contains one); view details about the map; share, print, and measure the map; and find locations on the map. Signing in to Map Viewer with an ArcGIS account may reveal additional options for adding layers, performing analysis, getting directions, and so on. Maps embedded in websites and shared through apps often contain a focused set of tools for a specific purpose, such as collecting information, editing features, or comparing two maps side-by-side.
Web maps can be used across ArcGIS because they adhere to the same web map specification. This means you can create web maps in one ArcGIS app and view and modify them in another. For example, you can create a web map in ArcGIS Pro and your colleague can modify it in ArcGIS Online.