The idea is while in a Direct Message (DM) Voice/Video call, to be able to "Pop-Out" the DM from Discord and also be able to view other DMs/servers at the same time.
Example: The video/voice call begins, a user can select to "Pop-Out" the DM from Discord, (Similar to how on Twitch, you can "Pop-Out" the chat.) The user can then proceed to viewing other Discord servers/DM(s) while still having the video/voice call DM "Popped-Out", without having the user going back and forth from the DM call to other Discord servers/DMs/Etc.
I recommend this feature because I personally would rather chat with my voice with someone one-on-one, while he/she chats via messages. So instead of going back and forth from the DM call and seeing what he/she wrote, I'll always have it "Popped-Out" while still doing other things on Discord.
Thank you for reading/listening! I appreciate it.