A Linux stream is data traveling in a Linux shell from one process to another through a pipe, or from one file to another as a redirect.
Streams can travel through several Linux stream-pipe connections of incremental commands to accomplish administrative tasks. Characters in Linux streams are either standard input (STDIN) or output (STDOUT) from a file or process, or error output streams from commands given to the Linux shell (STDERR). In the Linux command line interface, operators like pipe (|) and redirect (< and >) control input and output streams.
Streams are created by entering characters from a keyboard. Different Linux commands, such as sed, allow users to manipulate the stream text, in this case editing the stream.