Anything you might need a server for. What apps do you use?

You can't use the cloud as a workstation, and you don't use "the cloud" directly for anything. The cloud is the group of physical servers which contains the servers (usually virtual servers) you put there.

You can use a public cloud like, or a private cloud that you set up in your office IT room, that you manage yourself.

"cloud storage" is the idea of having a file server "out there" somewhere, all that is is file storage.

There's something I don't understand about your question. I thought I had answered everything in my posts above. What sort of things do you need to do with your mobile clients?