css only show on hover code example

Example 1: hover over something to make html visible

div {
    display: none;
}
    
a:hover + div {
    display: block;
}

Example 2: on hover display another div css

.showme {
  display: none;
}

.showhim:hover .showme {
  display: block;
}


<div class="showhim">HOVER ME
  <div class="showme">hai</div>
</div>