What a subdomain is
A subdomain is the part before your main domain name. In blog.example.com, the word blog is the subdomain of example.com. It lets you run a separate site or service under your brand without registering a new domain, which is useful for things like a help centre, an app, or a documentation site.
Subdomains are configured through DNS and can point to entirely different systems from your main site, while still feeling part of the same organisation to visitors.
Subdomain or subfolder
A common decision is whether to put content on a subdomain or in a subfolder like example.com/blog. For SEO, subfolders often keep authority consolidated more simply, since search engines treat them as clearly part of one site, which affects your domain authority and overall SEO.
Subdomains make sense when a section is technically distinct, such as an app or a tool on different infrastructure, or when it genuinely needs to stand apart. The right choice depends on the use case rather than a blanket rule.
Practical notes
Each subdomain needs its own configuration, including its own SSL certificate so it is served over HTTPS. Plan your URL structure across domain and subdomains so the whole estate stays coherent.
We advise clients on whether a subdomain or subfolder fits their goals, then set up the DNS, certificates, and hosting so it works cleanly.