A "cloud provider" is a company that offer cloud computing—typically, Infrastructure as a Service (IaaS), Software as a Service (SaaS) or Platform as a Service (PaaS)—to other businesses or individuals. Cloud providers are sometimes referred to as cloud service providers or CSPs.
In Orbitera, a "cloud account" is generic. For example, in Google, a cloud account is called a GCP project. In Microsoft Azure, it's an Azure subscription. In AWS, it's a linked account. All of these generically are the lowest common denominator of usage charges that cloud providers make available.
Conceptually, you can think of an Orbitera customer as a bucket that can contain cloud account usage charges, thus enabling you to manage billing across multiple channels. You can assign one or many cloud accounts to a customer, then pool or aggregate usage across multiple cloud providers.
You can have a 1:1 customer-to-cloud account relationship, or a 1:many customer-to-cloud account relationship.
This is good for you as a provider of cloud software, because you can make your software available on multiple clouds, your customers can access your software from these different clouds, and you can provide one integrated bill to your customer for all usage charges. If your customer accesses your software from multiple channels/clouds, you can present a unified bill.