By looking at the name itself you can understand the idea behind the creation of these domain names, .com and .net. But later on due to heavy growth of Internet and Internet users, it became unmanageable and both Top Level Domain names (TLD) opened to public without any constrains.
Originally .COM is for commercial purpose and .NET is for network related organizations typically ISPs were using .NET. The guidelines for domain registration were outlined in RFC 1591, (Request for Comments 1591).
Those days these guidelines were strictly maintained by an organization called Network Solutions. Registrations of domain names were rejected if they do not comply with RFC 1591. And as mentioned above with the heavy load of demands, processing of these domains became unmanageable task.
.COM
As per RFC 1591- this domain is intended for commercial entities, that is companies. This domain has grown very large and there is concern about the administrative load and system performance if the current growth pattern is continued. Consideration is being taken to subdivide the .COM domain and only to allow future commercial registrations in the sub-domains.
.NET
As per RFC 1591 – this domain is intended to hold only the computers of network providers, that is the NIC and NOC computers, the administrative computers, and the network node computers. The customers of the network provider would have domain names of their own (not in the NET TLD).
Network organisation’s businesses became blurred and the internet growth caused the process of reliable validation of organizational types extremely costly and still not fools proof. Consequence of this is the opening of .COM and .NET for anyone/registrants to choose as per their wish.
Users can register domain names from any registrar which are accredited by ICANN (Internet Corporation for Assigned Names and Numbers). The registry receives registration information from each domain name registrar authorized to assign names in the corresponding TLD and publishes the information using a special service, the WHOIS protocol. Nowadays users can request for private domain name registration where WHOIS information will not be public viewable. This is being offered for additional charges.
Recap:
.COM and .NET are TLD names available and open to anyone these days. But, nowadays even a business or network company prefers .COM, since it’s most popular among the users and simply get registered in people’s mind. Except non-profit organizations most of the organizations prefer .COM as their first priority in domain name registration. But large organization registers both domain names and points to same server or using .COM for web related activities and .NET for email purposes. Technically there is no difference between .COM and .NET