I'm not looking to sell any of my business, but I've always wondered when watching shows like Shark Tank, are they selling existing shares that they personally own, or is it understood that they will just dilute all the existing owners by issuing new shares?

As a follow up implication from that, if they are buying existing shares, how would the company even get any of that money? Wouldn't all that money go to the person selling, not the company?

Sometimes it sounds like they are talking about selling a personal share, for example when there are already investors that might be dilution protected. In those cases how would the company even utilize that money?