1) "net" is one of the top-level domain name s that can be used when choosing a domain name. It generally describes the entity owning the domain name as an organization that administers or provides network connection services. Along with the second-level domain name (for example: "mhv" in mhv.net), the top-level domain name is required in Web and e-mail addresses.
For more information, see gTLD (generic top-level domain name).
2) Net (capitalized or not) is sometimes used as a short form for "Internet."