You can add ArcGIS Server services, OGC WMS services, and KML documents. You can also add features you create with the map viewer and features from a delimited text file or GPX file on your computer. You cannot add layer packages or other types of ArcGIS for Desktop content.

Features stored in the map come from creating a map notes layer or adding a file to the map and can only be edited by the map author. Features from feature service layers are streamed from a web service and can be edited by users if the service administrator allows it.

It depends. If you have large amounts of data and you have access to ArcGIS for Server, an effective approach is to create a feature service and add it as a layer to your map. You should also add feature layers if you want others to edit the features and their attribute information. By default, your features will be editable for anybody viewing your map.

If you do not have access to ArcGIS for Server or if you only want to add a handful of features, add a map notes layer with the map viewer. It is easy to create a few features this way, and the map viewer provides several templates from which you can pick shapes and symbols. However, it's not practical to add large numbers of features since you have to create each one within the map viewer—you cannot, for example, upload a file of predefined features. These layers are read-only, so others cannot change the features or edit related attribute information.

If you have features in a delimited text file (.txt or .csv) or a GPS Exchange Format file (.gpx), you can import them into your map. This is a convenient way to add features you have stored in a file on your computer. Once you've added them to your map, you can change the symbols and configure pop-ups.

If your file contains many features, you should place it on a web server and reference it through a URL using Add Layer from Web, rather than importing it directly into the map.

If you see a time slider at the bottom of a map, that map includes one or more temporal layers, and you can play the map to see how the information changes over time.

Save updates an existing map you own. Save As creates a copy of the map, and you see the original Save Map window where you can update the title, tags, and so on. You can save a copy of any map that is not owned by you; you cannot update an existing one you do not own.

Think of the map viewer as a canvas onto which you can easily mash up different layers that interest you. Once you've created a map, you can share it with other portal users or embed it in an app. This might be an app that you wrote using ArcGIS Web APIs or, if you have little programming experience, it could be a preconfigured app such as the portal's web app templates.

ArcGIS Web APIs can also be used to build a mashup from scratch without starting in the map viewer. This involves more code and layer management by the developer.

You can share supported types of maps, apps, layers, tools, and files.

Yes. Content items, search results, and groups can be accessed directly by a URL. For more information on sharing URLs, see Link to content.

The items are still in the website. However, you may have to change the site setting to show ArcGIS desktop content. By default, the site only shows web content in search results, groups, and the gallery. This means that if you haven't set the site to show desktop content, your layer packages and other data files won't appear in search results or your groups.

By default, the portal website only shows you content that can be opened in a web browser. To see layer packages and other desktop content in search results, groups, and the gallery, set the site to show all content. Click the arrow to the right of Show: Web Content Only at the top of the website and click All Content from the drop-down list. For more information, see Show ArcGIS desktop content.

An ArcGIS map is a set of informational layers and pop-ups covering a certain geographic area. The map is interchangeable such that it can be viewed in a browser, mobile device, or desktop app. You can use app-specific tools to change the map extent, find places, and see detailed data about a location.

You build a map by defining an area of interest, choosing a basemap, adding data layers, and configuring pop-ups. You can save maps and share them with everyone or with specific groups to which you belong.

A web app is a website that combines maps, data, and tools for a targeted use such as finding polling stations for an election. It might be as simple as a navigable map image embedded in a blog or as complex as a GPS navigation visualization.

Web apps can be based on templates (included with the portal) or developed from scratch using the ArcGIS Web APIs. Both of these types of apps can plug in to ArcGIS maps. In general, apps are constructed from information in maps, supplemented with specific configurations and customizations. Apps can be hosted as a part of your content in the system or they can be managed independently and registered with the system.