OBS (Open Broadcaster Software) is a free and open-source software for video recording and live streaming. Discord is a popular voice and text chat app for gamers. To get OBS to hear your Discord audio, you need to set up a virtual audio cable.
A virtual audio cable is a software that creates a virtual audio device that can be used to route audio between different applications. This allows you to send the audio from Discord to OBS, even if your Discord and OBS are running on different computers.