LAN Cable Distributor (Network Coupler), Y-Adapter

Designed for use in pairs to allow two internet connections through one cable.

Two internet cables from the router go into the first splitter,
then the splitter connects the two internet cables into one internet cable (for example, a cable routed through the wall).
The second splitter on the other side reconnects the cable into two, allowing two different devices to connect to the internet.

The described scheme can also be seen in the product images.