bash - Piping and Redirection

Question

What is exact difference between piping and redirection?

Where should we use piping and where should we use redirection?

How they internally work?

Answer 1

Redirection is (mostly) for files (you redirect streams to/from files).

Piping is for processes: you pipe (redirect) streams from one process to another.

Essentially what you really do is "connect" one standard stream (usually stdout) of one process to standard stream of another process (usually stdin) via pipe.

Pipes have also the synchronization "side effect" : they block one process (on reading) when the other has nothing to write (yet) or when reading process cannot read fast enough (when the pipe's buffer is full).