A physical “drive” is a storage device that is somehow interfaced with the computer. In a workstation, a physical drive is usually a hard disk drive. In a netbook, a physical drive is usually a solid-state storage device (without any moving parts).
In the case of a server, however, an individual hard disk drive is usually only a component of a disk array. A disk array (such as RAID, redundant array of inexpensive drives) managed by a specialized controller serves the same purpose as a single hard disk in a desktop computer.
Yet another type of “drive” is a RAM (random access memory) drive. Such a drive is made up of memory locations. This means that any content in a RAM drive disappears when a server powers down.