Newbie question: Cash flow vs Profit

[Daniel Lascalles]

Hey all! I've been just lurking and learning, but now I need help to clarify some terms. I thought I understood the concepts, but when I read this blog by David Greene and another on Bigger Pockets versus what other websites tell me, I got confused. Are they saying the same thing, but I'm just getting caught up in semantics?

E.g:

David Greene: "Cash flow is defined as how much money is leftover after all expenses are paid on a rental property."

Isn't that profit? 

Quickbooks: Profit is defined as revenue less expenses. It may also be referred to as net income. Cash flow, on the other hand, refers to the inflows and outflows of cash for a particular business.

BalancesMB: Cash flow is the money that flows in and out of the firm from operations, financing, and investing activities.

Thanks for your help!