This listing is for a 2x pack set of Network combiner cords (Ethernet). This is used primarily in office environments if you only have one horizontal run of cable and want to plug in two devices using the same cable run--most commonly seen is both a network jack for a office PC and another for a VoIP phone. It can be used at home if you have either a switch at both ends or a coupler/wall jack.
This item works well and is really for the person who doesn't want to run an extra cable for long distances. Please keep in mind that if you have Power-over-Ethernet (PoE) devices, those will not work with this setup as the network combiner/splitter uses what would normally be the Power twisted pairs for Data.