The Behringer U-Phoria UMC 1820 is an audio interface that allows you to plug in microphones and instrument to record onto the computer onto a DAW (digital audio workstation) software.
Each channel has a signal (green) and clip (red) light to let you know if you are getting signal and to let you know if your audio is clipping. Each channel you can select line or instrument input level. You can also select to pad ("PAD") the signal by -20 dB if needed, if the audio source is too loud.
The Behringer has two mic inputs controlled by gain 1 and gain 2. It also has phantom power when needed for condenser microphones.
On the patch panel, 3-8 control the gain knobs 3-8 on the Behringer correspondingly. You can plug in your instruments here.
There are two headphone jacks, both are 1/4 inch inputs. You can select to hear channels 1-2 and 3-4.
In whatever DAW software you are using, make sure the input and output are set to UMC1820. You can usually set this in Preferences, which would show up under the software name on the top menu bar.
For example:
The output of the Behringer is connected to the receiver amp which allows for the surround sound speaker system set up in the room. Learn how to mix your audio in surround sound! Link