The TP-Link TL-POE150S is a PoE injector and makes a regular network connector PoE compatible. This PoE injector has 1 gigabit Ethernet network input and 1 input for a power cable. You can, for example, connect an IP camera to these inputs. The TP-Link TL-POE150S then uses the network output to supply both data (such as camera footage) and AC power via a network cable. This is known as PoE.
Power over Ethernet (PoE) is a technology for providing voltage and data over 1 network cable. In other words, PoE makes an extra power adapter unnecessary. This is especially useful if you're using a network device, such as an IP camera, in an area without a socket.