For years, I thought that | (pipe) was a notation which connects the left side’s stdout to the right side’s stdin. For example,

% ls -t | head

ls’s stdout is connected to head’s stdin.

While it is semantically “okay” understanding, technically speaking, that creates a pipe in the first place. Then the pipe is connected to ls’s stdin and head’s stdout.

From pipe(7);

Pipes and FIFOs (also known as named pipes) provide a unidirectional interprocess communication channel.

This misunderstanding also made me really confused about named pipes. I simply didn’t get it. Now I know that a Unix pipe is a thing. Giving a filesystem presence for the thing makes sense.