Is there any restriction of sub-domains ?

You can host unlimited sub-domains. Sub domains are created on a DNS server and they don’t need to be registered with a domain registrar, of course, the original domain would need to be registered before a sub domain could be created. You can create any number of sub-domains with your doamin, for grouping the related information e.g support.cpwebhosting.net, forums.cpwebhosting.net.

Does Cpwebhosting.net does provide the Free Domain name or free hosting?

False Domain Names – Directory Listings – Free Hosting

Some providers may offer unique name under their own name like: www. primarydomain.com/yourcompany/

This is not a real domain name, it is a directory – and you should try to avoid it.

These URLs are not desirable, especially for companies. Try to avoid them if you can afford to register a domain. Typically these are more commonly used for personal sites and free sites provided by your ISP, you may have seen www .primarydomain.com/~username as a common address, this is just another way to share a single domain and provide users their own address.

Open competition in domain name registration has brought about a dramatic decrease in pricing so domain sharing is far less common since people can register their own domains for only $8.95 per year.

One of my friend does not want to keep his registration, will I be able to register it.

yes, this is another source for domain registrations – expired domains.
When somebody register a domain, think of it as a rental, assuming there are no legal or trademark issues with the domain name, he/she is free to use it as long as he/she continue to pay the yearly fee. Now a days you can also register in advance as many as 10 years). Some people register domains as speculators, hoping that they can later sell them, while others may have planned to use a domain and never had the time. The result is that domains that were previously registered regularly become available for registration again. If you wish to register an expired domain you pay the same fee as you would for a new registration. You can also get from your friend, as it expires, you just register with your own name.

If my domain name is transfered,Will my email and website still work the same once?

Yes, your website and email will work the same. You will have to reconfigure your email accounts and there may be some minor changes that need to made to your files with regards to paths. But everything should function normally.

I want to know what is ICANN . I see all this stuff about ICANN accredited, but what is that?

ICANN stands for “Internet Corporation For Assigned Names and Numbers”

The Internet Corporation for Assigned Names and Numbers (ICANN) is an internationally organized, non-profit corporation that has responsibility for Internet Protocol (IP) address space allocation, protocol identifier assignment, generic (gTLD) and country code (ccTLD) Top-Level Domain name system management, and root server system management functions. These services were originally performed under U.S. Government contract by the Internet Assigned Numbers Authority (IANA) and other entities. ICANN now performs the IANA function.

What is a Top-Level Domain (TLD)?

A top-level domain is the suffix that is attached to the end of a Domain Name. .com, .net and .org are Top-Level Domains in the hierarchical Domain Name system. In the Domain Name ‘cpwebhosting.net‘, the .net is the Top-Level Domain. Top-Level Domains are the highest-level category of Internet names.

What is a Registry?

A registry is a company or organization that maintains a centralized registry database for the Top-Level Domains. Currently there is only one Registry for every Top-Level domain, .com, .net and .org. NSI Registry maintains this Registry.

thanks tcheck, I have one more question,What is a Registrar?

A registrar is an ICANN accredited company or organization that is authorized to provide registration services for the top-level domains such as .com, .org and .net. Registrars have contractual agreements with their customers.

A Registrar submits all newly registered domains into the Registry.

What is the difference between a Registry and a Registrar?

A registry provides direct services to registrars only, not Internet end-users. The Registry database contains only Domain Name service (DNS) information (Domain Name, name server names and name server Internet Protocol [IP] numbers) along with the name of the Registrar that registered the name and basic transaction data. It does not contain any Domain Name Registrant or contact information.

A Registrar provides direct services to Domain Name registrants. The Registrar database contains customer information in addition to the DNS information contained in the registry database. Registrars process name registrations for Internet end-users and then send the necessary DNS information to a Registry for entry into the centralized Registry database and ultimate propagation over the Internet.