What is the meaning of
The value of said property is adjusted automatically according to the content or the context of the element.
For example, a block-level element with
height: auto will grow taller as it contains more text. For another example, a block element with
margin: 0 auto will have the left and right margins increased until it becomes centered along the y-axis of the viewport.
It really depends on the property you give the value to, different properties behave differently depending on the content and context.