What is .......... IP Addressing?

The Internet Protocol (IP) is the principal communications protocol used for relaying datagrams (packets) across an internetwork using theInternet Protocol Suite. Responsible for routing packets across network boundaries, it is the primary protocol that establishes the Internet.

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Source : http://en.wikipedia.org

2) What is it?

It stands for Internet Protocol address. It is an unique address that identifies a computer on a network such as the Internet.

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Source: http://www.teach-ict.com/technology_explained/ip_addressing/ip_addresses.html