Some slicers have the ability to send prints to a printer over a USB connection. Others will require the print to be moved to the printer and printed from an SD card, or send through another software package.
We will call these "Print Senders". These package primary purpose is to provide some limited manual control of the printer, along with sending files to the printer over USB.
Files sliced in Simplify3D can be sent directly to the printer using the built-in serial connnectivity.
PronterFace is a simple GUI which allows you to manually heat, move, and send files to a 3D printer over a serial (including USB) connection.
This is a very widely used tool in the open-source community.
OctoPrint is indeed a sender, but operates differently from others such as PronterFace. OctoPrint provides a web interface which can be used to control a printer over the network. It is easily installed on an Raspberry Pi and provides a lot of flexibility in how a printer can be used.
This is used on the internal computer on the Xeed printer to provide the GUI to the screen as well as the web interface.
When installing this on a machine, it is greatly preferred to use Raspberry Pi controllers, for which pre-configured OctoPi distributions are available.
TeraTerm is not really a print sender, but is purely a terminal. This can be used for very simple manual interaction with the printer's console (GCODE) commands, and for debugging when you want to be sure the sender isn't filtering any communication to/from the printer.