the.com/subdomain
the apartment number on the internet's street address.
means a prefix attached to a domain name that creates a separate, addressable section of a website, like blog.example.com living under example.com.
from emerged with the domain name system in the 1980s, when engineers needed a way to subdivide one registered domain into functional zones without buying more real estate.
free and infiniteyou can create thousands under one domain name
dns recordeach one usually needs its own dns entry
seo debategoogle sometimes treats them as separate sites entirely