In computer and networking technology, an octet represents an 8-bit quantity. Octets range in mathematical value from 0 to 255. The term octet is also used in other contexts, such as in musical performance, to refer to a group of eight people or parts.
Networks: Bit – Byte – Octet – Part 1
All modern computer systems implement a byte as an eight-bit quantity. Octets and bytes are the same thing from this perspective. For this reason, the two terms are used interchangeably.
Historically, however, computers have supported bytes with different numbers of bits; octets and bytes mean different things in this context. Network professionals began using the term octet many years ago to maintain this distinction.
Computer engineers often use the term nibble when referring to an amount of four bits (half of an octet or byte) rather than calling it a half octet (or quartet, as is common in the music industry).