NAS is an external storage device attached to an IP network, usually a LAN, which allows users to store and access data from other devices. NAS is the next evolution of Network File Sytem (NFS) and Common Internet File System (CIFS).
NAS devices are ideal for giving multiple users remote access to large amounts of data. They can store multimedia files such as images, video, audio and documents, and act as a backup and restore device, among other tasks. See also Storage Area Network (SAN)