JSFiddle - React, Tailwind, and code Playground

HTML

<div>Some text that shows all the time
  <span class="more"> (more)</span>
  <span class="expanding"> and some more text that shows when you hover</span>
</div>

CSS

.more      { display: block; }
.expanding { display: none; }
div:hover > .expanding { display: block; }
div:hover > .more      { display: none; }