what are grep patterns called
grep is a command-line utility for searching plain-text data sets for lines that match a regular expression. Its name comes from the ed command g/re/p (globally search a regular expression and print), which has the same effect: doing a global search with the regular expression and printing all matching lines. Grep was originally developed for the Unix operating system, but later available for all Unix-like systems.
First appearing in Version 4 Unix, grep was created by Ken Thompson as a standalone application adapted from the regular expression parser he had written for ed (which he also created). In ed, the command g/re/p would print all lines matching a previously defined pattern.