What is browser and text zoom means?

I cant understand what “Browser and Text zoom should be at 100%” means in Change the Font Size of an Element challange.Help pls

Your code so far

  .red-text {
    color: red;
  h1 { font-size: 16px; } 

<h2 class="red-text">CatPhotoApp</h2>

<p class="red-text">Kitty ipsum dolor sit amet, shed everywhere shed everywhere stretching attack your ankles chase the red dot, hairball run catnip eat the grass sniff.</p>

<p>Purr jump eat the grass rip the couch scratched sunbathe, shed everywhere rip the couch sleep in the sink fluffy fur catnip scratched.</p>```
**Your browser information:**

Your Browser User Agent is: ```Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.167 Safari/537.36```.

**Link to the challenge:**

If you’ve never changed the zoom of your browser, then it’s probably at 100% already. That note is just in there because some people like to zoom in or out and their tests will fail even if the code is correct.

Depending on your browser, you’d see something like this if zoom isn’t 100%.