The border property can be used to visually define a page element's outer edge.
In CSS, the border property's value requires three parts:
thickness: Sets the thickness of the border, using pixels, ems, or rems.
type: Sets the border type. Common options are
dashed. There are many others.
color: sets the border's color, using named colors, HEX, or RGB values.
The CSS below gives a paragraph element a solid black border that is 2 pixels thick:
border: 2px solid black;