What's this sharepoint online ? cloud etc ?

The entire server infrastructure is hosted and maintained by Microsoft for you. This model removes the administrative overhead of SharePoint and lets the business focus just on using the power that is SharePoint. (While this might be great for the business, it does eliminate the need for a SharePoint administrator, so many of us will consider this license option the
enemy.)

There are actually two models to consider with SharePoint Online: shared and dedicated. The shared model provides you with a slice of a shared farm and enables you to use SharePoint out of the box. Server-deployed code and customizations are not permitted.

The dedicated model enables you to run your own farm, and you are allowed to make approved customizations to the server. Any change must be packaged in a solution package and validated by Microsoft before being deployed to the server. All licenses are bought per user.