Melissa Coates (Coates Data Strategies) has published an updated end-to-end diagram of Power BI. This is extremely useful to someone who would like to learn, understand and to present the capabilities of Power BI to any potential client.
She is generous to let us use the PDF version of this diagram. Find it here: Updated Version of the Power BI End-To-End Diagram.
Please remember to give her a shout out.