What is the difference between a top-level domain and a second-level domain?

In the Internet's Domain Name System (DNS), the domain name structure is clearly layered, and each layer has its specific function and meaning. Understanding the difference between top-level domain names (TLDs) and second-level domain names is essential for selecting and managing domain names. This article will introduce the main differences between top-level domain names and second-level domain names in detail.

Top-level domain name (TLD)

1. Definition and function:

The top-level domain name is the top-level domain name in the domain name system, located at the rightmost part of the domain name. It is the highest level in the entire domain name structure and is used to identify the type, region or organization of the domain name. For example, in "example.com", ".com" is the top-level domain name.

2. Type:

Top-level domain names are mainly divided into the following categories:

-Generic top-level domain names (gTLDs): such as .com, .net, and .org, these domain names are usually not restricted by geography or industry.

-Country and region top-level domain names (ccTLDs): such as .cn (China) and .uk (United Kingdom), used to identify specific countries or regions.

-Infrastructure top-level domain names: such as .arpa, mainly used for Internet infrastructure.

-Sponsored TLDs: such as .edu (educational institutions), .gov (government agencies), managed by specific organizations.

-Brand TLDs: such as .google, .apple, registered specifically for brands and businesses.

3.Registration and Management:

Top-level domains are usually managed and supervised by the Internet Corporation for Assigned Names and Numbers (ICANN) and its designated registry. The registration process usually involves selecting an available top-level domain and paying the associated fees.

Second-level domain

1.Definition and function:

The second-level domain is located below the top-level domain and is usually used to specify an organization, company, or a specific sub-website. It is the middle part of the domain name, immediately following the top-level domain on the left side of the domain name. For example, in "blog.example.com", "blog" is the second-level domain.

2.Structure and examples:

-Structure: The structure of a second-level domain is usually a combination of the top-level domain and the second-level domain. For example, "example" in "example.com" is the second-level domain.

-Example:

-Corporate website: In "www.example.com", "www" is the second-level domain name.

-Subsite: In "shop.example.com", "shop" is the second-level domain name, which is used to identify a specific subsite or service.

3. Registration and management:

Second-level domain names are usually created and managed by the owner of the top-level domain name. Organizations or individuals can create and configure second-level domain names in the control panel of their domain name registrar. This usually involves specifying the purpose of the second-level domain name, such as subsites, email servers, etc.

Main differences

1. Position and hierarchy:

-Top-level domain name: The rightmost part of the domain name, representing the top-level domain name classification.

-Second-level domain name: Located to the left of the top-level domain name, as part of the domain name, it is usually used to identify a specific organization or subsite.

2. Registration and control:

-Top-level domain name: Managed by ICANN and the registry management agency, usually requires registration through a registrar.

-Second-level domain name: Created and managed by the owner of the top-level domain name, does not require separate registration, and is usually configured by the domain name owner in his or her control panel.

3. Functions and uses:

-Top-level domain name: used to identify the type, region or industry attributes of a domain name.

-Second-level domain name: used to subdivide and organize domain names and create specific sub-sites or services.