Jethro Manager is an on-premise web based product, that should be installed on a Linux machine, and used by the user through a web browser. 
The server on which Jethro Manager is installed, doesn't have to be the same as of the Jethro query machine it is serving, but it is recommended to use them both on the same machine, as the configuration steps are a bit more easy.

Having said that, Jethro Manager can also be installed on one Jethro query node, and connected to a different Jethro query node. The communication between the Jethro Manager machine and the second Jethro query machine would be carried out by using SSH protocol (for enhanced security) and JDBC connections.