In the terminal, standard output defaults to the user's screen.
Stdout in the command pipeline
In bash, sequential commands can connect by pipes, represented on the command line by a vertical bar ("|"). Pipeline commands are processed left-to-right, with the standard output (stdout) of each command connecting to the standard input (stdin) of the next.
For instance, in this pipeline of two commands:
fortune | cowsay
The program fortune, which normally prints a random quotation to the user's screen, instead connects its output (stdout) to the input (stdin) of the command on the right:
For more information about standard output, see redirection in bash.