This device is designed to convert signals between different types of network media, specifically copper-based Ethernet (10/100/1000M) and fiber optic cables.
It allows for extending network distances beyond the limitations of copper cabling and can also be used in environments with high electromagnetic interference.
The model shown is a 10/100/1000M SFP Media Converter, which means it supports Gigabit Ethernet speeds and uses SFP (Small Form-Factor Pluggable) modules for the fiber connection (though the unit itself is "Without SFP AC220V," indicating the SFP module is sold separately.