Nmap Module

can Someone explain to me why these are used for ports scan
I mean why you need them

--packet-trace 
-Pn 
-n 
--disable-arp-ping

–packet-trace: Show all packets sent and received
-Pn: Treat all hosts as online – skip host discovery
-n: Never do DNS resolution
ARP ping scans are the most effective way of detecting hosts in LAN networks.