The answer below mentioning explainshell.com doesn't explain the `-Pn` parameter. This one makes nmap skip host discovery and immediately start the port scan. The developer of nmap discourages using this parameter:
https://twitter.com/bonsaiviking/status/1286024550241767426Only if you know the host is alive and at the same time does not want to be seen, then it may make sense to use it, otherwise it messes with nmap's rate calibration.
The website also doesn't really explain why those switches were chosen.
And it's not clear to me either: unless you lack permissions or you find yourself in some other special circumstances, `-sS` is superior over `-sT` (as the man page explains). The latter creates a full TCP connection, while the former sends only a SYN packet and waits for the response: SYN-ACK means port open, RST means port closed. Then it moves on, leaving the half-opened connection dangling.
`--min-rate` was chosen to increase speed, but it comes at the cost of accuracy. `-T4` is the better switch to increase speed. See the man page for details.