what does box-sizing in css do code example

Example 1: textarea { -webkit-box-sizing: border-box; -moz-box-sizing: border-box; box-sizing: border-box; width: 100%; }

textarea {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;

    width: 100%;
}

Example 2: box-sizing border-box vs content-box css

box-sizing:content-box;
	"Default. The width and height properties (and min/max properties) includes only the content. Border and padding are not included"
box-sizing:border-box;	
	"The width and height properties (and min/max properties) includes content, padding and border"