The first time the slash symbol was used is not known, as it has been used throughout history in various forms. However, it is believed that the use of the slash symbol as a punctuation mark began in the Middle Ages, where it was used as a symbol for the Latin word "per" which means "by" or "through". Over time, the slash symbol evolved to have a variety of uses in different languages and writing systems, and it has become a standard part of modern punctuation.

The Slash is most commonly used as the word substitute for "or" which indicates a choice (often mutually-exclusive) is present.

The Slash symbol can also be used to denote choices or alternatives (e.g., "and/or"), fractions (e.g., "1/2"), and line breaks in poetry (e.g., a line break between two lines of a poem). It is also used as a separator in dates (e.g., "11/10/2020") and URLs (e.g., "www.example.com/page").

Overall, the slash symbol is a versatile and widely used punctuation mark that helps to convey meaning and clarity in writing.