Windows 10: cables

Hello
I have a gateway which has two ports for phone plugs at the top. There is a tan phone (? connector) at the top which plugs in to one of these ports of the gateway and the other gateway port is empty. One phone line runs from this tan device to the wall and the other to a splitter. This splitter sends one line to the printer/ fax and the other line to a phone recorder.
Why can't the two phone ports be used instead of this connector?
What is this connector at the top called and what purpose does it serve?
I would have plugged one wire to the fax/printer from one of the ports and the other to the splitter for both the wall and also the recorder, eliminating the tan device.
Is this device in the port because the wall line has to be involved in the setup so that two separate cables cannot be used and the tan device therefore has to be used?

:)