Standalone systems are often systems used primarily within the field by sales people, surveyors, field engineers etc. This setup benefits people who need to have access on sites where they cannot gaurantee the availability of 3g, 4g, wireless or any other type of internet access.
When the standalone systems are reconnected to the internet they will synchronise back with the main server and any jobs that they've completed will be passed up. Any new jobs that are ready for them will be sent down along with any updates to the system should they be available.