What is a bit?
A bit is the smallest unit in digital representation of information. A bit has only two values, ON and OFF where ON is represented by 1 and OFF by 0. In terms of electrical signals a 1 (ON) is normally a 5 volt signal and a 0 (OFF) is a 0 volt signal.
What is a nibble?
A group of 4 bits are referred to as a nibble.
What is a byte?
In the world of computers and microcontrollers, 8 bits are considered to be a standard group. It is called a byte. Microcontrollers are normally byte oriented and data and instructions normally use bytes. A Byte can be broken down into two nibbles.
What is a word?
Going bigger, a group of bytes is known as a word. A word normally consists of two and sometimes more bytes belonging together.