VPS is an abbreviation of Virtual Private Server. This type of web hosting plan is more expensive than shared hosting but still cheaper than dedicated hosting. With VPS, some of the resources are communal, but not all. Memory and CPU time are shared amongst those on the server, but certain shares of said resources are allotted to each domain. This gives you greater computing power or flexibility in the case of traffic surges.
The answer is simple – despite having many different names, all of these companies belong to the same German AttractSoft group. That may not necessarily mean something evil – it could be that each service is just meant to cater to a different market and/or audience. For example, Awardspace is more popular in the US and India, while Netfirms is a well-known name in Canada.
Registries and registrars usually charge an annual fee for the service of delegating a domain name to a user and providing a default set of name servers. Often, this transaction is termed a sale or lease of the domain name, and the registrant may sometimes be called an "owner", but no such legal relationship is actually associated with the transaction, only the exclusive right to use the domain name. More correctly, authorized users are known as "registrants" or as "domain holders".
Many services offer so-called unlimited or unmetered service for whatever amount of bandwidth, disk storage and sites you use. It's important to understand that most terms of service actually do limit the definition of "unlimited" to what's considered reasonable use. The bottom line is simple: if you're building a pretty basic website, unlimited means you don't need to worry. But if you're trying to do something excessive (or illegal, immoral or fattening), the fine print in the terms of service will trigger, and you'll either be asked to spend more or go elsewhere.