AGNC Investment (AGNC -0.96%) is a mortgage real estate investment trust (REIT). That is an important fact to remember as you consider its astonishingly high 16% dividend yield. One really interesting fact about the company is that it literally tells investors what the stock is worth every quarter. And investors keep paying more than that price for the stock. Here's what you need to know before you buy this high-yield mREIT.What does AGNC Investment do?AGNC Investment is a mortgage REIT, which is vastly dif ...