Div in HTML is the container to that defines a section. Div container can contain many elements grouped together. This is done to apply a particular style to the section.
You can put the form in a separate container by wrapping it around div element.
Similarly the paragraphs, navigation bar etc are different containers that can be wrapped around a div.
<div id="form">
<form action="/submit_data.php">
<input type="radio" id="male" name="gender" value="male">
<label for="male">Male</label><br>
<input type="radio" id="female" name="gender" value="female">
<label for="female">Female</label><br>
<input type="submit" value="Submit">
</form>
</div>
Now at the time of styling which will be done using CSS, we can style the div and the style will be applicable to the container.