In computer science, binary numbers are used to represent data because computers only understand two states: off (represented by 0) and on (represented by 1). Each digit in a binary number is called a bit, and a group of 8 bits is called a byte. Converting binary numbers to decimal numbers is simple. You start from the rightmost digit, with the value of 1, and double the value for each digit as you move left. For example, the binary number 1010 is equivalent to the decimal number 10 (1x2^3 + 0x2^2 + 1x2^1 + 0x2^0). Binary numbers are fundamental to computer operations, as they allow for easy manipulation of data through logical operations like AND, OR, and XOR. Understanding binary numbers is crucial for anyone looking to delve into the world of computer science.