some of us doesnt understand the topic, but it might be me, could someone clarife that?
Lets go back to the beginning. When some banks got into trouble a few years back, governments bailed them out. They poured in tax payers money to shore up the balance sheet so that the banks where solvent. This was widely considered a bad thing, as it rewarded the banks for years of poor risk management (thats the raw nub, alot of other opinion is political and i'd rather leave that), and the presented us with a moral hazard.
We have a banking system that assumes (because it is told so) that they will backed by nation governments if they get into difficulty. The object of that government backing is actually to assure the population their deposits are safe, but it had come to be extended to the whole of the bank beyond depositors. So banks took risks they wouldn't otherwise have done, lent money to those they shouldnt, or underpriced debt etc.
So the solution, to instruct the banks that actually that's not how its going to be. The depositors will be secured, as was always intended to be the case, but if they get into difficulty the first port of call isnt the government/central banks, but the owners of the bank and its principle debt, bondholders. They reap the rewards, so they have to bail-in their assets to shore up the balance sheet. by converting their debt to equity, or by buying more equity in a rights issue, they refund the balance sheet to remain solvent. Its all about the balance sheet.