ELI5 The Suit - how did it become universal as business attire for men?

How did business suit and tie become the standard men’s attire for business? How did it become a global fashion standard? Who was Beau Brummel? Why was he central to the story of the business suit? Practically, what is the slash pocket for? Why do some shirts have cufflinks? ... 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: whackshackblackjack, shadojuggalo, iprotein, syntaxvorlon, derpling42, przasu, brinlong, blipsman, veryawesomeguy and timothygonzalez. 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]