Every item within the playlist contains a chain, if this is Checked in Green then the Chain is enabled, if it's unchecked in Red then the Chain is disabled. This is what is used to control the flow of the playlist.
When an item has Chain disabled (unchecked in Red), PlayoutONE will stop after playing that item and will wait until the Play Next button is pressed (this is located on the top of the Playlist window)
If an item is has Chain enabled (checked in Green), when the item finishes it will keep on playing through the rest of the Playlist.
To change the chain of an item, simply click on the chain check-box for that item, and it will alternate between Enabled or Disabled.
If you are running with Automation On, any Chains disabled (unchecked in Red) that are in the playlist will be ignored