nginx `listen` configuration generated by Mozilla SSL Configuration Generator -

i use mozilla ssl configuration generator(https://mozilla.github.io/server-side-tls/ssl-config-generator/) generate configuration.

my selections nginx , modern,the configuration has piece of code this:

server {     listen 80;     listen [::]:80;      return 301 https://$host$request_uri; } 

questions:

1、there 2 listens,what difference between them?
2、do not need add server_name in server block？

1. there 2 listens, difference between them?

one listen ipv4 on port 80 , other ipv6 on port 80. need second 1 when want use ipv6

2. not need add server_name in server block

yes should define server_name names website should reached on. if want allow www or non-www should change below

return 301 https://$host$request_uri; 

to

return 301 https://example.com$request_uri;