What does the decimal number 255 mean in binary?

255 as a decimal number (also known as a base 10 number) = 11111111 in binary (also known as a base 2 number). In binary, each digit is known as a bit, and 8 bits are known as 1 byte. 255 is the largest (positive) number you can make in binary using only 8 bits (1 byte).