NIDS and HIDS are types of Intrusion Detection System.
Network intrusion detection system (NIDS): NIDS operates at the network level and checks the traffic from all the devices connected in the network. It identifies specific patterns and abnormal behavior.
Host intrusion detection system (HIDS): It monitors only the system data and identifies suspicious activity on an individual host. HIDS takes snapshots of the system files, and if they change over time, it raises an alert.