— Data type: vm_task_t

This is a task_t (and as such a mach_port_t), which holds a port name associated with a port that represents a virtual memory map in the kernel. An virtual memory map is used by the kernel to manage the address space of a task. The virtual memory map doesn't get a port name of its own. Instead the port name of the task provided with the virtual memory is used to name the virtual memory map of the task (as is indicated by the fact that the type of vm_task_t is actually task_t).

The virtual memory maps of tasks are the only ones accessible outside of the kernel.