Ask Andy: What is a coco bond?

After two days of dramatic falls, shares in Deutsche Bank rebounded on Wednesday after reports that the bank was considering an emergency bond buyback scheme.

The bank's move is unlikely to involve so-called contingent convertible bonds, known as coco bonds, but there's a been a lot of chatter about their role in the latest share slide.

They have nothing to do with either beans or a warm bedtime drink, so what are they?

Our economics correspondent, Andy Verity has the answer.