clear definition of -u about photon HOT 1 CLOSED

Domains

example.com is domain name, it is the website's identity which makes it different from example1.com or example2.com.

Sub-domains

www.example.com is a subdomain. You can create as many as subdomains you want on a domain and people use it keep their stuff separated. For example, I may publish my blog at blog.example.com, host my ftp server at ftp.example.com and the main website at www.example.com.

URLs

http:// & https:// are URL schemas and every URL must have one.
https:// is just a secure version of http://.

Photon requires a root URL i.e. a domain or subdomain followed by http:// or https://.
If you don't specify the URL schema, Photon will automatically try to detect it.

from photon.