The so-called domain names, such as the google.com we choose, are generally the first-level or more top-level domain names without WWW. The www. we use is actually a second-level domain name, but we are used to using it as the default primary domain name. Here, what we need to introduce is the second-level domain name and the third-level domain name.
The second-level domain name and the third-level domain name are common concepts in the Internet, and the difference between them is mainly reflected in the hierarchical relationship of the domain name structure:
1. Second-level domain name
Second-level domain refers to a level below the top-level domain, usually used to indicate the classification of individual channel content. For example, in the domain name “blog.example.com”, “blog” is the second-level domain name.
2. Third-level domain name
The third-level domain name refers to a level below the second-level domain name, also known as a sub-domain name. It can be used to further divide and organize different sections or subprojects of the website. For example, in the domain name “rs.blog.example.com”, “rs” is the third-level domain name.
It should be noted that the level of the domain name can be increased or decreased according to actual needs. In addition to the second-level and third-level domain names, there may also be more sub-domain names, such as fourth-level domain names, fifth-level domain names, etc., but such cases are relatively rare.