Tag <legend>

<form action="/action_page.php">

 <fieldset>

  <legend>Personalia:</legend>

  <label for="fname">First name:</label>

  <input type="text" id="fname" name="fname"><br><br>

  <label for="lname">Last name:</label>

  <input type="text" id="lname" name="lname"><br><br>

  <label for="email">Email:</label>

  <input type="email" id="email" name="email"><br><br>

  <label for="birthday">Birthday:</label>

  <input type="date" id="birthday" name="birthday"><br><br>

  <input type="submit" value="Submit">

 </fieldset>

</form>