Our number system, decimal, has ten digits which can be used to represent any number. Have you ever asked yourself why we need ten digits in our number system. When we run out of digits we just start using the next column. Binary is a number system which uses just two digits - zero and one.
A bit is a single binary digit. It can either be a zero or a one.
A byte is a set of 8 bits that represent a single character in the computer's memory. While bits are often used to measure data transfer speeds, bytes are used to measure file sizes, hard disk space, and computer memory. Larger amounts of data are measured in units such as megabytes, gigabytes, and terabytes. For example, one kilobyte is equal to 1,024 bytes.
A word is simply 2 bytes.