The backslash is not really an English punctuation mark. It is a typographical mark used mainly in computing. It is called a "backslash" because it is the reverse of the slash (/) or forward slash.
The backslash is used in several computer systems, and in many programming languages such as C and Perl. It is commonly seen in Windows computers:
Do not confuse the backslash (\) with the slash (/) or forward slash.
Although it is not really an English punctuation mark, the backslash is included on these pages for completeness.