LAN: LAN, also known as Local Area Network,is a communications network that serves users within a limited geographical area, for example a building or a university campus. It is controlled by a network operating system and uses a transfer protocol.

WAN: WAN, Wide Area Network, is a long distance link used to extend and connect remotely-located LANs (local area networks.)

RAID: RAID is short for Redundant Array of Independent Disks. It is used to organize two or more hard disks in a manner as though they were one. The data is shared or replicated in such a disk and used to achieve greater capacity, reliability, and speed.