Part of macOS
installdApp installer
○ Leave it
Installs and removes apps and system updates.
What it is
Does the installing when you add an app or apply an update.
Why it might be busy
During an app install or a macOS update. Usually a few minutes.
If you stop it
The install stops part-way. Leave it until it finishes.
The verdict
○ Leave it. Part of macOS, or something that starts again by itself. You never need to close these.
In Activity Monitor
installdsystem_installdinstallcoordinationdinstallcoordination_proxyuninstalldappinstalld
From Procession’s guide, in the words the app shows.