A service takes your GIS resource, such as a map, tool, or geodatabase, and makes it available to a wider audience on ArcGIS Server. ArcGIS Desktop is designed to help you share your work with others as a service.
The way that you publish a service varies based on the GIS resource type. The table below highlights how to begin the publishing process in ArcGIS Desktop:
If you want to publish a map document...
...open the ArcMap document and choose File > Share As > Service from the main menu.
If you want to publish a geoprocessing model or tool...
...browse to a successful result of the model or tool in the Results window, right-click it, then choose Share As > Geoprocessing Service.
Beginning at 10.4, only administrators can publish a geoprocessing service. To allow publishers to publish geoprocessing services, see Change geoprocessing service and service extension publishing privileges.
If you want to publish something else, such as a geodatabase or address locator...
...browse to the item in ArcCatalog or the Catalog window, right-click it, then choose Share As Service.
From this point you have three choices:
Publish a service—If you're ready to publish, you can go through the entire process of connecting to the server and publishing a service. You can save your work as a draft service at any time and come back to it.
Save a service definition file—If you want to set up all the properties of a service and transfer them to a separate machine for publishing, you can create and save a service definition file. This is occasionally necessary in cloud environments, in secure environments, or when the server is not immediately available.
Overwrite an existing service—If you want to overwrite an existing service with an updated GIS resource and ancillary data, select this option.