I don't understand the @media query

Tell us what’s happening:
Create a media query for screens smaller than 800px in width. In that media query, create a #gallery img rule and set the width property to 50% . This will convert your gallery to a two-column layout.

  **Your code so far**
/* file: index.html */
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Photo Gallery</title>
  <link rel="stylesheet" href="./styles.css">
</head>
<body>
  <div class="header">
    <h1>CSS FLEXBOX PHOTO GALLERY</h1>
  </div>
  <div id="gallery">
    <img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/1.jpg"/>
    <img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/2.jpg"/>
    <img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/3.jpg"/>
    <img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/4.jpg"/>
    <img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/5.jpg"/>
    <img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/6.jpg"/>
    <img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/7.jpg"/>
    <img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/8.jpg"/>
    <img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/9.jpg"/>
    <img src="https://cdn.freecodecamp.org/curriculum/css-photo-gallery/10.jpg"/>
  </div>
</body>
</html>
/* file: styles.css */
* {
box-sizing: border-box;
}

body {
margin: 0;
font-family: Arial;
background: #EBE7E7;
}

.header {
text-align: center;
padding: 32px;
background: #E0DDDD;
}

#gallery {
display: flex;
flex-direction: row;
flex-wrap: wrap;
justify-content: center;
align-items: center;
padding: 0 4px;
}

#gallery img {
width: 25%;
height: 300px;
object-fit: cover;
margin-top: 8px;
padding: 0 4px;
border-radius: 10px;
}

@media (max-width: 800px)
  **Your browser information:**

User Agent is: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.114 Safari/537.36

Challenge: Step 20

Link to the challenge:

You’re off to a good start. Media queries are enclosed in curly braces, so you’ll want to add an opening and closing curly brace after the selector. Then, inside the curly braces you add the other CSS rulesets you want to include in the media query.