Web applications are powerful, database-driven pieces of software that can do really just about anything that you can think up.
Web applications can include simple functional systems such as a newsletter or calendar system to a complete employee intranet or patient extranet.
The maximum potential is when you combine these sorts of systems so that they all pull from a central data repository of patient related data such as medical history, lab and radiology reports, etc.
Typically these systems manage all scheduling and resource allocation via the same system that tracked patient records, histories, inventory, accounting, etc.
Once any information was put into the system, it would always be there to be accessed (in whole or in part) but other people using other aspects of the system.
Of course, security and permission is crucial when dealing with patient and other sensitive information, these web applications have to be HIPAA compliant.
The entire system can be managed and operated from anywhere on the web, so any computer, smart phone, or other web-enabled device could interact with the system at any time.
Medical users and patients need no significant infrastructure to use web applications, No issues with incompatible systems. The entire database and application is entirely online, requiring both local and remote backup services so that redundant backups can be maintained.