should have corresponding descriptions and definitions in the ArcGIS Online documentation here: What can you add to ArcGIS Online?—ArcGIS Online Help | Documentation . Currently there is not a 1:1 description of what is listed in the "Item Type" filters in ArcGIS Online and what is described in the online help documenation. Its difficult to help someone, especially a new GIS user, navigate all the language describing the content that is created when a person makes a Story Map, for example, or wishes to add content to ArcGIS Online.
I feel this idea is somewhat related to @Joshua Damron's idea Data Management - Working Notes on Items. His idea about working notes indicates having the ability to see what items go into creating a certain web map, app or layer. Having consistent documentation can help with data management and governance as there will be more clarity about what items go into a Story Map, or Survey123 application, for example. There are a number of layers, maps and items that go into building those products and new users may not even be aware of this. Knowledge of their interdependency is critical for good data stewardship and governance, and greatly helps out the site administrator if staff leave the organization.