If you do @nmap scanning with big exclusion lists, things are about to get a lot faster. ;)— Daniel Miller ✝ (@bonsaiviking) November 1, 2018
Both nmap and masscan are port scanners. The differences is that nmap does an intensive scan on a limited range of addresses, whereas masscan does a light scan on a massive range of addresses, including the range of 0.0.0.0 - 255.255.255.255 (all addresses). If you've got a 10-gbps link to the Internet, it can scan the entire thing in under 10 minutes, from a single desktop-class computer.
How massan deals with exclude ranges is probably its defining feature. That seems kinda strange, since it's a little used feature in nmap. But when you scan the entire list, people will complain, with nasty emails, so you are going to build up a list of hundreds, if not thousands, of addresses to exclude from your scans.