Nested virtualization is when you run a hypervisor (like Virtualbox) on a host PC, then you install a guest OS and
install a second hypervisor in that guest, then run another guest OS inside that guest

support for nested hardware-virtualization on Intel CPUs (starting with 5th generation Core i, codename Broadwell

KVM support available
pokud chci mit ve VIRTUAL BOXU zaplnuty v sekci SYSTEM/PROCESOR vlastnost "Enable Nested VT-x/AMD-V"