What is a SLD (Second Level Domain)?

I just wrote about the TLD, so this naturally follows:

A SLD includes the TLD name and further identifies the owning organization of a URL.

Second-level domains can be divided into further levels. These subdomains sometimes represent different computers within an organization, but are many times the same machine with different aliases.

Examples:

www.giantgeek.com
mail.giantgeek.com

TLD =  .com
SLD = giantgeek.com
Subdomains = www.gianteek.com & mail.giantgeek.com

NOTE: Refer to HTTP/1.1 for details on how IP addresses, routing and webservers are impacted by this.

Interesting enough, some one character SLD’s do exist,  x.com for example.

References:

Cheers!

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