The paragraph below is an *official* answer taken from devfest.info
GDG DevFests are large community-run events that
can offer speaker sessions across product areas, all-day
hack-a-thons, codelabs etc.
Each GDG DevFest will be inspired by and uniquely tailored to the
needs of the developer community that hosts it. But while no two
events will be exactly alike, each GDG DevFest will, at its core, be
powered by a shared belief that when developers come together to
exchange ideas, amazing things can happen.
Target audience for the GDG Bandung DevFest are professionals and students including web and mobile developers of all skill levels building applications using Google technologies.