ELI5 Upper and Lower Case - why do some letters look so different?

Why do some letters have a completely different character when written in uppercase vs lowercase (e.g. A/a, R/r, E/e), whereas others simply have a larger version of themselves (e.g. S/s, P/p, W/w)?   ... We explain like i'm five!   Thank you to the r/explainlikeimfive community, and specifically the following reddit users whose questions and responses formed the basis of this conversation: thegrog1603, r3dd170rx, shmiggles, thehooligan95, whistleridge & varron   To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected] ... we love hearing from you!