Use of name attribute

**i got the program but i’m not understanding the use of name attribute

  <p>Click here to view more <a href="#">cat photos</a>.</p>
  <a href="#"><img src="" alt="A cute orange cat lying on its back."></a>
  <p>Things cats love:</p>
    <li>cat nip</li>
    <li>laser pointers</li>
  <p>Top 3 things cats hate:</p>
    <li>flea treatment</li>
    <li>other cats</li>
  <form action="/submit-cat-photo">
    <input type="text" placeholder="cat photo URL" required>
   <label for="indoor">
      <input id="radio" type="radio" >indoor
    <button type="submit">Submit</button>
      <input type="radio" >outdoor

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User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.84 Safari/537.36.

Link to the challenge:

When you read the lesson provided with the challenge , you can see

  <input type="radio" name="indoor-outdoor">Indoor 

this input element has a name attribute set to indoor-outdoor