What are filter command in Linux?

Linux Filter commands accept input data from stdin (standard input) and produce output on stdout (standard output). It transforms plain-text data into a meaningful way and can be used with pipes to perform higher operations.

How do I filter a directory in Linux?

Filter files by name in a directory using grep

This is the easiest way to find files (and folders) on Linux systems. grep is a program that is shipped with all Linux and FreeBSD systems (and even macOS). grep is used for filtering data using regular expressions.