Comment by waste_monk

You're thinking of the Guest Additions which is part of the base Virtualbox package and free for commercial use.

The (commercially licensed) Extensions pack provide "Support for USB 2.0 and USB 3.0 devices, VirtualBox RDP, disk encryption, NVMe and PXE boot for Intel cards"[1] and some other functionality e.g. webcam passthrough [2]. There may be additional functionality enabled by the Extension pack I cannot find at a glance, but those are the main things.

[1] https://www.virtualbox.org/wiki/Downloads [2] https://www.virtualbox.org/manual/ch01.html#intro-installing