A short one: say you need to enter a credential into a shell variable which is running in as a sub-process in emacs. One example would be PASSPHRASE when using duplicity. This is how to do it without leaving the passphrase in bash history and without it being echoed:

read -p "password:" PASSPHRASE

The -p sets the prompt to for the read command to be “password” which is recognised by Emacs and the text that the user enters is not echoed into the buffer.