The CSS Box Model is a box that is wrapped aroung every HTML element. It includes: margins, borders, padding and the actual content.

padding is the space between the content and the border, whereas margin is the space outside the border. Also, top/bottom margins are collapsible.

Height and width properties are used to set the height and width of an element. The height and width can be set to auto (this is default. Means that the browser calculates the height and width), or be specified in length values, like px, cm, etc., or in percent (%) of the containing block

'padding: 25px 50px' means that the top and bottom paddings are 25px while the left and right paddings are 50px.

Outlines do not take up space; Outlines may be non-rectangular; Borders support rounded corners; Border has several properties to style each side; Outline supports offset.