In the URL `https://support.google.com/help`, the part labeled 'support' is known as the _____.

In the given URL https://support.google.com/help, the term 'support' refers to the subdomain. A subdomain is a subset of a larger domain and it allows for a more organized structure of a website. In this case, 'support' is used to categorize the content offered by Google, indicating that this section of the website is specifically for support-related resources.

Subdomains can help enhance user navigation and allow for specific services or content to be distinguished from the main website. For example, this structured approach allows Google to create a dedicated space for support, which can house help articles, FAQs, and direct assistance, separate from the other services they provide under the main domain 'google.com'.

The other terms in the context of the URL have different meanings: the main domain refers to the primary address of the website without any prefixes; a resource locator typically refers to the complete URL itself; and the path, which comes after the domain, specifies the particular location of a resource or service on the server. Thus, 'support' is best categorized as a subdomain in this context.