Exit tax?

Can someone simply explain to me the concept/principle of exit tax? I have no shares, but 100% shares in an LLC in the USA. Source KPMG "The German tax authorities treat the move as a fictitious sale of your shares and tax the increase in value up to that point (the "hidden reserves") immediately, even if you haven't sold the shares at all." How does it all work? How does the tax authorities calculate the damage (lol)? Why does something like this even exist? submitted by /u/jimmyglo