What is the use of <label>?

HTML-CSS
1

Label;
“Represents a caption for an item in a user interface”

Sorry if this is a bad question but why does this site teaches to constantly using label inside form?

I noticed that label here is used for repetitive codes, but why?

  <form action="/submit-cat-photo">
    <label><input type="radio" name="indoor-outdoor"> Indoor</label>
    <label><input type="radio" name="indoor-outdoor"> Outdoor</label><br>
    <label><input type="checkbox" name="personality"> Loving</label>
    <label><input type="checkbox" name="personality"> Lazy</label>
    <label><input type="checkbox" name="personality"> Energetic</label><br>
    <input type="text" placeholder="cat photo URL" required>
    <button type="submit">Submit</button>
  </form>

Would be nice to also explain why “for” and “id” used here(and suddenly stopped using them in next tutorials)

<form action="/submit-cat-photo">
    <label for="indoor"><input id="indoor" type="radio" name="indoor-outdoor"> Indoor</label>
    <label for="outdoor"><input id="outdoor" type="radio" name="indoor-outdoor"> Outdoor</label><br>
    <input type="text" placeholder="cat photo URL" required>
    <button type="submit">Submit</button>
  </form>
</main>