There are a number of capabilities that you can add or remove from your site. This gives you greater control over your site's functionality. Within your site's Capabilities tab in the administrative application, there are both standard options for you to enable or disable.
The standard capabilities are fully developed and stable options for your site.
The API Explorer is another tab on your dataset pages which gives your users an integrated way to explore the Geoservices API, generate queries, and access the responses. This can be useful for users of your site to understand how the data can be programmatically accessed and build system integration using your ArcGIS data.
If you have PDFs or other document links, like Word documents or external URLs, this capability will display their content within the site. If this option is disabled and users select document links on your site, the content will open in a new tab or download in the browser.