The protocol HTTP / HTTPs is used to send information. HTTP(s) is a secure connection and has aSSL-certificate associated.
Subdomains WWW. SHOP. or BLOG. are subdomains. You can decide for yourself what your subdomain should be.
SLD (Second-Level Domain) is the primary domain name. It will be the unique name you register.
TLD (Top-Level Domain) Coming after the primary domain,.dk is the Danish. The order of a domain will go through the country's internet orginization..DK is managed by dk-hostmaster.dk