ELI5 Bank Runs - why does a run on the bank happen?

What is a run on the bank? Why it can happen in a fractional reserve banking system? What’s the best thing to do when there’s a bank run? When was the first bank run? Can we prevent bank runs? ... we explain like I'm five Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion. To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Join us on Twitter: https://www.twitter.com/eli5ThePodcast/ or send us an e-mail: [email protected]