Introduction:
A single binary digit is known as a bit. It is the most basic unit of information in computing and digital communications. The term 'bit' is a contraction of "binary digit," and it represents the smallest amount of information that can be stored or processed in a computer system.

Explanation:
The binary number system is a base-2 numeral system that uses only two digits, 0 and 1. Each digit in the binary system is called a bit. Here's a detailed explanation of the answer:

Bits and Bytes:
- A bit is a single binary digit, representing either a 0 or a 1. It is the fundamental unit of information in computing.
- A byte, on the other hand, is a group of 8 bits. It is the basic storage unit in computer systems and is commonly used to represent characters. For example, the letter 'A' can be represented by the binary value 01000001, which is 8 bits or 1 byte.
- While a bit can only represent a single binary value (0 or 1), a byte can represent a larger range of values, from 0 to 255.

Units of Data Storage:
- When dealing with larger amounts of data, we use larger units of storage.
- Kilobytes (KB) is a unit of storage that represents 1024 bytes.
- Megabytes (MB) is a unit of storage that represents 1024 kilobytes or 1,048,576 bytes.

Conclusion:
In summary, a single binary digit is known as a bit. It is the smallest unit of information in computing and represents either a 0 or a 1. A byte, on the other hand, is a group of 8 bits and is commonly used to represent characters. When dealing with larger amounts of data, we use units such as kilobytes (KB) and megabytes (MB).