More on a global minimum tax

I have no idea what he's talking about, and I get the feeling that he doesn't either. President Obama declared today that:

no American company should be able to avoid paying its fair share of taxes by moving jobs and profits overseas. From now on, every multinational company should have to pay a basic minimum tax. And every penny should go towards lowering taxes for companies that choose to stay and hire in the United States of America.

This appeared in his state of the union address, but it still doesn't make any sense. How does the United States tax every multinational with a basic minimum tax?  What the heck does that even mean?  They're multinational.  How can you tax them?  I fully suspect that this is as nonsensical as it seems, but John Hayward is under the impression that it's some sort of tax that other countries agree to employ.  Either way, it's par for the course, I'm afraid.