Delphi XE with Firebird Database, Datasnap Driver, DataSnap Service vs other schemas when working with mobile apps [on hold]

I`ve found out that most of the time it is recommended to use this schema when connecting to a localhost server.

Not necessarily Firebird as Database, but the Driver and the Service are always recommended to be Datasnap.

The most important question is: why Datasnap instead of others?

Then I have some questions to go around that one and might also be answered if that one is.

I might be missing some client-server architecture concepts. Wich are those concepts?

Why to use a Datasnap service instead of, E.G., the Firebird service that runs by default in the database host server? Is creating the Datasnap server a really required extra feature?