The CSS outline property is a shorthand property for setting one or more of the individual outline properties outline-style, outline-width and outline-color in a single declaration. In most cases the use of this shortcut is preferable and more convenient.
The outline-color CSS property sets the color of the outline of an element. An outline is a line that is drawn around elements, outside the border edge, to make the element stand out.
The outline-offset CSS property is used to set space between an outline and the edge or border of an element. An outline is a line that is drawn around elements, outside the border edge.
The outline-width CSS property is used to set the width of the outline of an element. An outline is a line that is drawn around elements, outside the border edge, to make the element stand out:
The outline-style CSS property is used to set the style of the outline of an element. An outline is a line that is drawn around elements, outside the border edge, to make the element stand out.