align-items : what is the difference between flex-start and Stretch?

.container {  height: 500px;  padding: 10px;  margin: 50px auto;  background: #eee;  display: flex;  align-items: flex-end}.container .box {  padding: 10px;  width: 200px;  height: 200px;  background-color: #fff;}

<div class="container"><div class="box"></div></div>