[realslimjd]

I've worked places that have used Carta for this. Sometimes the company buys the shares back, but I think the more common case is that it's new investors. You do get a check, but it's separate from your regular one. Sales like this are long term capital gains, so they're taxed differently than your regular income. No you cannot trade it for shares of something else [0].

[0] - There are investment vehicles (exchange funds) that do this for publicly traded stocks. They're a good way of diversifying your portfolio if you're heavily weighted in one stock, but they typically keep that capital locked up for seven years which is not great if you value liquidity.