JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box">
  <span class="tooltip">какой то текст</span>
</div>

CSS

.box {
  width: 200px;
  height: 200px;
  background: red;
}

.tooltip {
  display: none;
  position: fixed;
}

.box:hover .tooltip {
  display: block;
}

JavaScript

var tooltip = document.getElementsByClassName('tooltip')[0];

window.onmousemove = function (e) {
    const x = e.clientX,
        y = e.clientY;
    tooltip.style.left = (x + 10) + 'px';
    tooltip.style.top = (y + 10) + 'px';
    
};