what is the difference between HIDs and NIDs?

Hello,
I searched "what is the difference between HIDs and NIDs" and I got below result:
Quote:

Host-based intrusion detection systems (HIDS) are also known as host-based IDS or host intrusion detection systems and used to analyze events on a computing device rather than the data traffic that passes around the computer. HIDS mainly operates by taking and looking at data in admin files (log files and config files) on the computing device that it protects. Network-based Intrusion Detection System is also known as network IDS or NIDS used to examine the network traffic. A network intrusion system has to include a packet sniffer to gather network traffic for further analysis.

I have some questions:
1- To protect an Apache or any web server, NIDS used?
2- Is the HIDS just useful for a local network and examine file changes and etc on the operating system? If yes, when an operating system using an Antivirus, then why HIDS?

Thank you.