What is the difference between visibility:hidden and display:none?

The CSS rules visibility:hidden and display:none both result in the element not being visible. Are these synonyms?

display:none means that the tag in question will not appear on the page at all (although you can still interact with it through the dom). There will be no space allocated for it between the other tags.

visibility:hidden means that unlike display:none, the tag is not visible, but space is allocated for it on the page. The tag is rendered, it just isn't seen on the page.

For example:

test | <span style="[style-tag-value]">Appropriate style in this tag</span> | test

Replacing [style-tag-value] with display:none results in:

test |   | test

Replacing [style-tag-value] with visibility:hidden results in:

test |                        | test

They are not synonyms.

display:none removes the element from the normal flow of the page, allowing other elements to fill in.

visibility:hidden leaves the element in the normal flow of the page such that is still occupies space.

Imagine you are in line for a ride at an amusement park and someone in the line gets so rowdy that security plucks them from the line. Everyone in line will then move forward one position to fill the now empty slot. This is like display:none.

Contrast this with the similar situation, but that someone in front of you puts on an invisibility cloak. While viewing the line, it will look like there is an empty space, but people can't really fill that empty looking space because someone is still there. This is like visibility:hidden.