Let's start by viewing the sample ArcGIS Server services at http://sampleserver6.arcgisonline.com/arcgis/rest/services. When we request the page as HTML, we notice a few things. First, the version of ArcGIS Server is shown (version 10.21 at the time of writing). The version number is important because many features and bits of information may not be present in older versions. Secondly, we see a list of links pointing to folders. These are map services grouped in any way the publisher chooses. We also see a list of map service links below the folder lists. Finally, at the bottom of the page, we see supported interfaces. In this site, we can see the REST interface that we're familiar with. The other interfaces will not be covered in this book. Here's a picture of the service:
If we change the format of the REST Service request in our browser to Pretty JSON, by adding ?f=pjson
to the end of the URL, we can see roughly how the ArcGIS JavaScript API would see this location:
Here...