Just a link from story A to story B, or even to not-story Z (e.g. something on YouTube), which appears in story A as underlined text rather than as an embedded item.
It’s reasonably simple, pethaps the most difficult thing being the lack of agreed and understood terminology for all the parts.
Something that might require explanation is why Share / Copy to clipboard in the Medium app copies a title & space before the https: , like this
‘“100 Words” https://medium.com/@sjhtma/100-words-1f6205a9d1b4
Having to edit out the part before https: after Pasteing is what causes the trouble.
Are you with me yet?