To plan multiple services that are identical in service flow (or nearly identical), WP allows you to "link" services. A service that is linked to another will automatically inherit the service flow changes you make to the "master" service. A linked service can be "unlinked" to no longer inherit changes to the master service. But once the link is broken, it cannot be re-established.
Multiple services can be linked to a single master, and they do not have to be on the same day as the master.
If services are linked, you are given additional options when making changes to service details, as well as when scheduling roles and assigning people. While changing service details (message title, location, Bible passage, etc.), you'll be given the option to have any changes you make copied to the linked services. While adding roles and people, WP gives you the option to have them added to the linked services as well.
To link a service, it must be created as a linked service (and the master service must be specified). The pages used to create single services and series of services give you the option to designate linked services.