HTML <legend>: 양식 그룹 레이블 요소

<form action="">
  <fieldset>
    <legend>좋아하는 맹수를 골라주세요</legend>

    <input type="radio" id="tiger" name="beast" />
    <label for="tiger">호랑이</label><br />

    <input type="radio" id="lion" name="beast" />
    <label for="lion">사자</label><br />

    <input type="radio" id="cat" name="beast" />
    <label for="cat">고양이</label>

    <button>제출하기</button>
  </fieldset>
</form>

legend {
  background: #dddd;
  color: #000;
  padding: 3px 6px;
}