Part of macOS
mediaremotedNow Playing
○ Leave it
Shows what’s playing and lets you control it.
What it is
Runs the Now Playing controls in Control Centre and on the keyboard’s media keys.
If you stop it
macOS starts it again straight away. Leave it.
The verdict
○ Leave it. Part of macOS, or something that starts again by itself. You never need to close these.
In Activity Monitor
mediaremotedmediaremoteagentmediasharingd
From Procession’s guide, in the words the app shows.