This document discusses virtual machines and VirtualBox. It begins with an overview of virtualization software and terminology like host OS, guest OS, and virtual machines. It then covers advantages of virtual machines like portability, snapshots, and sandboxing. The document discusses installing Linux and Windows virtual machine images in VirtualBox. It provides details on different VirtualBox networking options like NAT, bridged adapter, and NAT network to allow VMs to communicate. It concludes with methods for file transfer between the host and virtual machines.