The cloud-only model
Cloud-only describes a situation where the service models you want to use (software as a service [SaaS], platform as a service [PaaS], or infrastructure as a service [IaaS]) run strictly in the cloud; there’s no connection to existing on-premises-based systems. One of the advantages of using the cloud-only model is that you don’t have to worry about the infrastructure that the services run on. All the backend functionality is invisible to your users and your IT department.
For smaller companies like startups or non-profits that don’t have in-house IT resources or capital to buy and maintain their own infrastructure, the cloud-only model, with its managed infrastructure, can be a good choice - you don't have to buy or manage the infrastructure because the cloud service provider (CSP) takes care of that. Note, however, that the cloud-only model can limit how much you can tailor your services, because your users and IT staff can't customize the SaaS and PaaS-based services running in the cloud.
If you need to be able to customize your services and infrastructure, you may need a hybrid model instead.