A SharePoint on-premises architecture is where SharePoint is only deployed on the on-premises infrastructure datacenter or on an IaaS cloud provider:

You can deploy SharePoint in several different topologies, such as completely on-premises or in Azure, but the basic architecture described in the hybrid scenario will have the same requirements for your on-premises infrastructure in your data center, or for Azure as an IaaS. You can see more at https://technet.microsoft.com/en-us/library/cc263199(v=office.16).aspx.