BigCommerce is a bit different from our other hosting plans in that it's a SaaS (software-as-a-service) provider instead of an IaaS (infrastructure-as-a-service) provider. In other words, rather than renting space on a virtual machine where you setup and configure your own site, BigCommerce provides you with an app you login to that creates and online store.
A web hosting account is a secure space on powerful computers (called servers) located in special buildings (datacenters) that provide consistently fast Internet connections, redundant power supply, and physical access security. Today, web hosting has evolved from being considered “just some space on a server” to being a comprehensive platform on which you can build, publish, and market your website, in addition to providing powerful collaboration tools such as email, calendars, and file sharing.
In terms of what many vendors call unlimited service, Web Hosting Pad's terms of service indicate that its definition of unlimited is what it calls "incremental." Basically, as you need more capability, it wants to discuss that with you, both to help you get the most out of its services, and to make sure you're using its systems without abusing them.