PPD - Return air and fresh air?

In video 3.1 air-based systems. Around min 8:30 the diagram is confusing. Based on that diagram the return appears to be the air that is drawn from outside. and the supply air is from the outside as well? can someone clarify?

@10-04-MS anyone have any insight on this that they can share?

@luis.torres - He is only showing general return air from the space for simplicity. What is missing is fresh air added to the return air, and exhaust air dumped. Here’s a diagram that illustrates the rest of the system:
(Source: https://blog.micrometl.com/what-is-a-hvac-power-exhaust-achieving-proper-ventilation/ )

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