ELI5 Smallpox - is it related to monkeypox?

How is monkeypox related to smallpox? Why was it possible to eradicate smallpox, when it’s been impossible to do for other diseases? Why do vaccines owe their name to smallpox? What is cowpox? How does chickenpox fit into all this? ... 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: jimmiekosmo, afinkawan, meerkatmanor987, gingercunt101, prasiatko, mikeevans1990 and jefetoro1234 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]