It’s pretty simple. If you own 10,000 shares of NVCN and they announce they are buying NVCN for $3/share, you’ll get $30k. Usually a buyout is announced before the close of the deal and the stock will typically jump to and trade around the buyout price. What’s nice about that is another company can offer a better deal and the price can jump again.
Sometimes when the deal closes, you’ll get cash. Sometimes you get shares in the new company. If that’s the case, using the above scenario, you’d get $30k worth of BSX stock.
Either way, it’s a good thing.