What is a Nvss or Cctv System? What All Parts One Need to Purchase When One Has to Install This System

What is a NVSS or CCTV system? What all parts one need to purchase when one has to install this system

NVSS connects to the internet and you can watch the property from anywhere, anytime.CCTV is on LAN and can be watched only locally.
What is a NVSS or CCTV system? What all things are involved [...]