In Web GIS one will work exclusively with “web service” type layers, mostly feature layer (sometimes you will see these as hosted feature layers).
Any content, you, as the author create and manage or use from your local ArcGIS Enterprise (used to be called Portal for GIS), finding web layers will be pretty easy and straight forward. If you are a “user” of map layers that you don’t manage or curate, then the layers need to be found.
As mentioned before, more and more organizations are using an ESRI-based Open Data portal to share their organizational data to the world. One isn’t (or doesn’t need to) go directly to a specific Open data site, find the data, they can can simply be in ArcGIS Online, their own organizational portal, Pro (and yes, even if you are still using ArcMap), can find and use web map layer by searching ArcGIS Online (even if you don’t have an AGOL account).
Everyone….Pro is here. It is essentially, the norm, except for organizations that have special needs such as 3rd party integrations, complex editing environments, etc. Any normal data management, map creating, publishing and overwriting data to the web can all be done in Pro. Do what you need to do to move on to Pro and get experience with ArcGIS Online and ArcGIS Enterprise (provided your organization needs/use it…its just like AGOL, but behind your firewall).
Any map layer that has been shared to the ESRI cloud and shared to “Everyone” (aka the world), one can “find” and then “use” a map layer within ArcGIS Online (or organizational portal), or Pro.
I will mention that, yes, you can “download”, save as a “shapefile,” file geodatabase feature class, then publish up to your own content, BUT THERE IS ABSOLUTELY NO NEED TO DO THIS!!!! unless the data set is huge, you don’t care about having to physically manage data changes every time the source data changes (which can be real-time, hourly, daily, etc)….do you really want to do this?! Probably not, so don’t go there. Learn and practice the methods to find web map layers and publish and overwrite organizational data to the web (either your internal portal (ArcGIS Enterprise) or ArcGIS Online.
Directly using web map layers “is the” easiest way to use map layers from other organizations (and your own, too), especially when used within your own organization. The PDF map, printed map is becoming obsolete and easily replaced with a more rich method of presenting and using map-based information (even showing metrics, stats, etc).
Now, on to Finding Map Layers (Data)…
Finding (Searching) for map layers (data) in ArcGIS Online, Enterprise, or Pro is similar to searching the Web. Type in keywords, hit return, review results, find the “best,” “correct,” “most authoritative” map layers to use. I have best, correct, and most authoritative in quotes because one has to “evaluate” (often look at layer descriptions and summaries, the publishing source, etc) to determine if the map layer you are interested in is the layer you “really” want to use. Just because you find one (likely many) similar/same map layers from one or likely multiple sources, doesn’t mean you actually want to use it….Many, many organizations, and people like you and I publish data and share to the world for the world to discover and find.
So, “finding” map layers is pretty easy to do, but actually identifying the layer(s) you want can be time consuming, but is super important when using information you do not control or curate. Be cautious, use critical thinking, review the data (which may involve reviewing the layer documentation, publishing source, the map layer and attribute table, values, codes, etc. You may even need to contact the source to determine authenticity, accuracy, and how current the map layer is. ESRI contains an “authoritative” tag that is helpful for those searching for map layers….however, even the same organization will have multiple layers for the same set of data as “authoritative.”
Finding and discovering map layers hinges on the publishing organization to provide useful and descriptive and commonly used keywords, summaries, descriptions, and feature layer names, including the proper use of the “authoritative” tag, and properly managing and quality controlling the map layers being published to the AGOL cloud and/or Open Data site….just as organizations “should” be writing and storing “metadata” with their information, this is now a bigger issue with publishing “authoritative” map layers to the world so others can “find” and “use” it.
Finding a Map Layer using ArcGIS Online (easier search)
Watch this short video to find a layer that is “easier” to find.
Finding a Map Layer Using ArcGIS Online (difficult search)
Same map layers are not obvious to search for and discover. Search difficulties arise because organizations don’t use common word as keywords (tags), lack or don’t use common and descriptive language in layer summaries and descriptions which provide the useful information to “find” map layers on the Internet. In addition, organizations can apply “authoritative” flags to their data sets. Organizations also are challenged with spatial data being managed, copied, used, and published by different departments and groups within the same organization. This contributes to the difficult of map layer discovery. This is a sign that organizations need to develop procedures, policies, and communications and collaborations to better coordinate spatial data management that the public can use. All organizations fail in this respect some of the times, but as more and more information are placed on the ESRI cloud, the easier it will be for the general public to find and use the “authoritative” map layers.
This video shows how one can search and discover for a layer that many not be so easy to search for.
This example shows a popular California state managed and published map layer called Cal Enviroscreen 3.0, can be searched for and ultimately added to ArcGIS Online. The simple “enter search terms, click Enter, pick the top search result” will not suffice.
CA Geoportal (Search on calenviroscreen 3.0)