-F (Fast (limited port) scan) Specifies that you wish to scan fewer ports than the default. Normally Nmap scans the most common 1,000 ports for each scanned protocol. With -F, this is reduced to 100. Nmap needs an nmap-services file with frequency information in order to know which ports are the most common (see the section called “Well Known Port List: nmap-services” for more about port frequencies). If port frequency information isn't available, perhaps because of the use of a custom nmap-services file, Nmap scans all named ports plus ports 1-1024. In that case, -F means to scan only ports that are named in the services file. -r (Don't randomize ports) By default, Nmap randomizes the scanned port order (except that certain commonly accessible ports are moved near the beginning for efficiency reasons). This randomization is normally desirable, but you can specify -r for sequential (sorted from lowest to highest) port scanning instead.

This is directly from nmap options summary @ CLI: -F: Fast mode - Scan fewer ports than the default scan

From nmap.org: -F (Fast (limited port) scan) Specifies that you wish to scan fewer ports than the default. Normally Nmap scans the most common 1,000 ports for each scanned protocol. With -F, this is reduced to 100.

The answer: -F (Fast (limited port) scan / Fast mode, scans fewer ports than the default scan)