A landline phone is an old style Analog phone that does not utilize the internet or cable to work. Your phone plugs directly into the wall jack and you have that phone line turned on with a phone number.
A hardwired phone is a phone that is plugged directly into a wall phone jack.
Some clients require that you have an analog landline with a hardwired phone. Please review the client opportunity announcement and the client checklist to see if a landline and hardwired phone is required.