This is meant to live on a glanceable monitor.
It is a means to preview different page formats on GOV.UK so that if there are any layout issues, they can be caught before deployment.
There are examples of lots of different formats across GOV.UK.
Go to govuk-previewer.herokuapp.com
Open each of the example formats in a new browser tab.
If using Chrome browser (recommended), use this in conjunction with two Chrome plugins: Revolver and Auto Refresh Plus which will allow for automatic tab rotation and refreshing at a specified interval.
(One Tab is also handy for saving/restoring these tabs if needed.)
Run browser in presentation mode — ⇧ ⌘ F