That's probably Safari or some other web view. You can get more detail using Activity Monitor. The Mac App Store version of EtreCheck cannot see all system processes. Activity Monitor won't show them to you either by default. But at least in Activity Monitor you can change the setting. Go to Activity Monitor > View > All processes.
As the name says, you will have to "monitor" it for heavy activity. EtreCheck just shows a single snapshot in time. It will be difficult to take the same exact snapshot in Activity Monitor. When you notice the fans working hard, look in Activity Monitor.
I don't see very much wrong with your computer. It seems a little bit too slow. Your file system performance is about twice as slow as it should be at 72 seconds. Maybe try to restart your Mac in Safe Mode, as instructed in this Apple Support article: How to use safe mode on your Mac - Apple Support. This is supposed to rebuild certain system caches. Otherwise, I don't see any opportunities to make any changes there.