An IP address is a unique number / address used to identify a device on a network. An IP address is made up of 32 binary bits, which is divided into a Network portion and Host portion with the help of a Subnet Mask.
The 32 binary bits are broken into four octets (1 octet = 8 bits). Each octet is converted to decimal and separated by a period (dot). For this reason, an IP address is expressed in dotted decimal format e.g. 192.168.10.12. 
The value in each octet ranges from 0 to 255 decimal, or 00000000 - 11111111 binary.