What it means in plain language
A subdomain is a part of the name placed before the main domain, which allows you to separate a separate area of the website or service.
Where it genuinely helps
A subdomain creates a separate area under the main domain and can divide apps, languages or environments while complicating DNS, cookies and analytics.
What to decide before acting
Use it when a service genuinely needs separate technical ownership rather than merely a convenient label.
How to tell whether it works
Check DNS, certificates, indexation, login sessions, cross-domain tracking and links with the main domain.
