Peter, you don't say what OS you are using but I will assume that it is fairly recent. You also don't say if you are or have ever used or experimented with the Home app or HomeKit.
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The changes made to System Preferences have confused many people including myself. When I get a new computer I go through the settings and turn off everything that I don't use so I don't remember what is on by default. The System Preferences window has a search box which I need to use since the method of organization there is opaque to me.
In System Preferences
1. go to (click on) the Apple ID setting on the top of the "table of contents"
click on iCloud
under "Apps Using iCloud" click on "Show All"
scroll down the list to find "Home" and, using the slider, turn it off
2. Similarly check this setting
Privacy & Security/Location Services/System Services/HomeKit
3. And..
Notifications (under "Application Notifications") turn off "Home"
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Of course if you are trying to use HomeKit then the answer is entirely different and I might have eaten lunch instead of writing this.? ;-)
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