On Fuchsia, a newly created process has nothing. A newly created process cannot access any kernel objects, cannot allocate memory, and cannot even execute code. Of course, such a process isn’t very useful, which is why we typically create processes with some initial resources and capabilities.
Most commonly, a process starts executing some code with an initial stack, some command line arguments, environment variables, a set of initial handles. One of the most important initial handles is the
PA_VMAR_ROOT, which the process can use to map additional memory into its address space.
Not the most detailed description just yet, but Fuchsia seems to be getting fleshed out more and more.