什么是外边距重叠，如何解决外边距重叠

margin的上下间距重叠问题现象：2个上下并列结构的时候,如果给上面的盒子添加了margin-bottom,同时给下面的盒子添加了margin-top,此时应该解析的垂直间距是2者之和,但是浏览器解析的时候,会按照最大数值去解析。

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    *{
      margin: 0;
      padding: 0;
    }
    .box1{
      width: 200px;
      height: 100px;
      background-color: red;
      margin-bottom: 100px;
    }
    .box2{
      width: 300px;
      height: 200px;
      background-color: blue;
      margin-top: 50px;
    }
    
  </style>
</head>
<body>
  <div class="box1"></div>
  <div class="box2"></div>
</body>
</html>

解决方法：A、给下面的盒子添加父元素且添加声明overflow:hidden;

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    *{
      margin: 0;
      padding: 0;
    }
    .box1{
      width: 200px;
      height: 100px;
      background-color: red;
      margin-bottom: 100px;
    }
    .box2{
      width: 300px;
      height: 200px;
      background-color: blue;
      margin-top: 50px;
    }
    /*解决box1和box2的上下间距重叠问题*/  
    .fuqin{
      overflow: hidden;
    }
  </style>
</head>
<body>
  <div class="box1"></div>
  <div class="fuqin">
    <div class="box2"></div>
  </div>
</body>
</html>