Outline means to draw a line around the element at the outside of the border.
Example
You can try to run the following code to implement the CSS3 outline-offset property −
<html>
<head>
<style>
div {
margin: 20px;
padding: 10px;
width: 300px;
height: 100px;
border: 5px solid pink;
outline: 5px solid green;
outline-offset: 15px;
}
</style>
</head>
<body>
<div>TutorialsPoint</div>
</body>
</html>