Characterized by or consisting of two parts or components. (Dictionary.com).
Binary is important mainly because it can be represented easily in electronics by either the presence or lack of current. Computers use binary for both their instructions and memory. Binary can also be useful for some math operations, known as bit-shifting. This is a much faster basic math than other systems, useful for speed-intensive programs such as games and calculation.
Binary Mode in FTP
See FTP for "Binary Mode".