SIM-format illustration. The embedded chip is installed inside a device; a travel eSIM is downloaded, not inserted as this chip. Image: Jbond2018; revised by En rouge / Wikimedia Commons, CC0. https://commons.wikimedia.org/wiki/File:SIM_card_sizes.png | https://creativecommons.org/publicdomain/zero/1.0/deed.en | Reused without editorial changes.
Read the related Korea Travel Desk guide: Korea Travel eSIM, SIM Card or Pocket Wi-Fi: How to Choose.