When we make an unvoiced sound,
we don’t use our voice.
Put your fingertips on your throat and say /p/- the last sound of verbs like help, stop, and hope.
You won’t feel anything, because you don’t use your voice to make /p/, do you? The /p/ is an unvoiced sound.
Some other examples of unvoiced sounds are /f/, /k/, /s/, /sh/, and /x/.