slash v. backslash

A slash (aka forward slash, aka stroke, aka virgule, aka solidus) is the punctuation mark consisting of a line drawn from the lower-left to the upper-right, like so: /

The slash serves several purposes:

• As a substitute for ‘and’ or ‘or’. E.g., ‘add one tablespoon of butter/margarine’. Another example of this usage is in the construction ‘and/or’, which can be construed as ‘and or or’, all of which is redundant, given that the word ‘or’ isn’t exclusive, meaning that it can imply ‘and’ all by itself.
• As a line break when quoting several lines from a poem, play, or song lyrics.
• Between the initial letters of words or between syllables in some abbreviations: 24/7, I/O, TCP/IP, a/k/a, n/a, w/o.
• To divide the numerator and denominator in a fraction.
• To denote a spare in bowling.
• As a path delimiter on Unix-like systems or in URLs.
• For various purposes in programming, including division and comments.
• As a command line option indicator.
• As a date delimiter.
• As a comma in ancient Rome.

A backslash (aka reverse solidus, aka slosh)  is drawn from the upper-left to the lower-right, and looks like this: \

The provenance of the backslash is considerably more recent, having been introduced into ASCII in 1961 by Bob Berner to allow for easy rendering of the /\ (AND) and \/ (OR) characters. Its use is confined almost entirely to computing, where it is most widely recognized as a path delimiter in DOS and Windows systems.

Wikipedia on slash

Wikipedia on backslash