Many of the capabilities in ArcGIS Online are included but some activities do consume credits.
Using credits: Storage
There are three types of storage that consume credits: feature storage, imagery storage, and file storage.
Storage is calculated by the size of features, files, tiles, scenes, and vector tiles your organization has stored in ArcGIS Online.
Using credits: Transactions
Transaction-based tools—such as geocoding, geoenrichment, image analysis, and spatial analysis—consume credits, and some of these tools are also available in other products.
Viewing maps and apps and sharing data do not incur credit charges. Here is a list of capabilities that consume credits.