In terms of what many vendors call unlimited service, Web Hosting Pad's terms of service indicate that their definition of unlimited is what they call "incremental." Basically, as you need more capability, they want to discuss that with you, both to help you get the most out of their services, and to make sure you're using their systems without abusing them.
To host a website on the internet, an individual or company would need their own computer or server. As not all companies had the budget or expertise to do this, web hosting services began to offer to host users websites on their own servers, without the client needing to own the necessary infrastructure required to operate the website. The owners of the websites, also called webmasters would be able to create a website that would be hosted on the web hosting service's server and published to the web by the web hosting service.
Moving to another website consists of transferring the website’s files and databases, configuring your site with the new host, and directing your domain’s DNS to the new host. Once you pick a new site host, they can usually help you out with this process. The cost will depend on the host you’re switching to, but it will probably be anywhere from $150-$400.