The on-premises Snaplex, or Groundplex, is a service installed on an end user's local machine that provides access to data both on premises, behind a firewall and in the cloud. The Snaplex can be installed anywhere on the end user network that has access to the required data or on premises application.
The advantage of using Snaplex on-prem instead of a cloud Snaplex is that data which resides on the end user data center can be accessed through SnapLogic pipelines. All pipelines and associated metadata are stored in the cloud by SnapLogic. When a pipeline needs to access data residing on premises, the pipeline can be run with a Snaplex on-prem runtime path.