A new one on me, Economics edition

See here for what I'm talking about.

My question: I always assumed that the bottom of the credit market was just zero. Is it really possible (in the real world rather than just in theory) to have negative interest rates? Wouldn't that mean that the lender gives you money and pays you extra money just for taking it? I don't see why anybody would do that!

I have to admit that I don't exactly understand what's going on with credit right now anyway - isn't credit supposed to be tight? Wouldn't that mean that interest rates are higher rather than lower? I know everything is very volatile right now and that's part of the answer, not to mention just that this is a very complex subject, but if anybody has a relatively simple explanation I'd love to hear it.