OneOps is a complex application that facilitates DevOps. As such it uses its own terminology and introduces its own concepts. Once you familiarize yourself with these concepts you are one step closer to understanding OneOps.
An organization in OneOps is a group under which various teams, clouds, assemblies, and services can be logically grouped. An organization can be your whole organization, a sub-unit of the organization, a single group inside the organization or any combination of those. You can create organizations to logically organize your projects, sub-projects, applications of all sizes.. In that respect organizations can also be various projects in your organizations. It is entirely up to you how you define an organization.
A user is a single user with a single login to whom you can assign permissions and responsibilities inside of OneOps. You can group various users into a team.
You can group various users into teams. You can logically group several users into cohesive teams to make management of your users simple. This also simplifies permissions. You can assign permissions to the whole team instead of individual users, for example, the development team, QA team, operations team, DevOps team, and so on.
Clouds are groups of common services that are offered under a common tag. By themselves clouds are nothing but a label and are not functional at all. They just act as an aggregator under which you can group various public (AWS compute, Azure compute, AWS DNS, and so on) or private (OpenStack) services. It is a good idea to give a descriptive name to the cloud. For example, if you are creating a cloud to group together some AWS services such as AWS EC2, Route 53 DNS, and S3 DNS, then it's a good idea to call it AmazonCloud instead of MyCloud.
As mentioned above, a cloud is just a tag and is of little use until you add a service to it. You can add a public service to it, provided you have a key, such as AWS EC2, or you can add a private service to it such as Nova Compute from OpenStack (if you have your own OpenStack installation).
An assembly, as defined by OneOps, is the definition of an application architecture and all its components including its infrastructure. OneOps provides a very visual way of defining an assembly. Assemblies are highly customizable and portable; once defined, they can be deployed to any target cloud without any more changes. Assemblies are defined by adding different platforms to them and defining relationships between them.