What is `box-sizing: border-box;` and why use it

Box-sizing is a CSS property that determines how the total width and height of an element is calculated. When using box-sizing: border-box;, the padding and border of an element are included in its total width and height. This means that if you set a width of 200 pixels, the actual content area will adjust to account for padding and borders, making it easier to manage layouts without having to calculate widths manually.

Using box-sizing: border-box; often simplifies layout design because it allows for more predictable sizing of elements. This is particularly useful when dealing with responsive designs or grid layouts.