You have been given a lot of information about ArcGIS Online, and it really only scratched the surface of this complex platform. After going through the sections and the exercise, you should have a good grasp of what ArcGIS Online is, how it is structured, how to create a web map, and how to publish a feature layer from ArcGIS Pro to ArcGIS Online. Again, it is recommended to go to the help documentation for ArcGIS Online, found at https://doc.arcgis.com/en/arcgis-online/, to learn more about the platform and its capabilities.
In the next chapter, you will build on what you learned in this chapter by utilizing Smart Mapping in ArcGIS Online.