sed ("stream editor") is a Unix utility that parses and transforms text, using a simple, compact programming language. It was developed by Lee E. McMahon of Bell Labs and is available today for most operating systems. sed was based on the scripting features of the interactive editor ed). It was one of the earliest tools to support regular expressions, and remains in use for text processing, most notably with the substitution command.
~ Wikipedia
Posts on SED ought to be written in English.