The unique address of a computer (server) to a local area network or the Internet, consisting of four whole numbers (from 0 to 255 in decimal notation) separated by periods, such as 18.104.22.168.
The numeric form addresses used by computers to human numerical address is inconvenient, so it is replaced by a domain name.
In hexadecimal ip address has eight octets, where each octet – a hexadecimal number from 0 to F, is considered the beginning of the right side.
For SEO ip-address is one of the key points, as the search engine is easy to determine which sites have the same ip and thus learn the true owners of a number of mirrors for them is easy. When creating the satellites must be assigned to each of them its own ip-address for safety and long life satellite.
Not all hosting identifies a number of ip addresses to their customers, and placed hundreds of sites on the same address, which is not always acceptable for SEOs.