What is the difference between a feature class, layer, shapefile?

[JesusMontalvo]

I see these terms interchangeably in different training and instructional material. 

[Egge-Jan_Pollé]

feature layer| Definition - Esri Support GIS Dictionary 

[JoshuaBixby]

As I mentioned, "most of Esri's documentation" defines feature layers as a web GIS construct.  Esri Support's GIS Dictionary is helpful, but it isn't authoritative, not even with Esri because it is a product of Esri Support and not Esri Development that actually designs and builds the products.

The more authoritative documentation on feature layers is:

• Feature layers—ArcGIS Online Help | ArcGIS 
• Feature layers—Portal for ArcGIS | ArcGIS Enterprise 

[BSplitt]

This is possibly one of the most helpful tutorials I've seen related to ArcGIS. Thank you so much.