Spotlight and Privacy
Do you, like me, use Spotlight a lot to find things on your computer? I search through my mail, my documents, my applications and lots more by simply clicking on the little magnifying glass and entering a couple of words. I am not usually searching the Web but my computer. It makes organising the files on my computer easy - well, it supports laziness!
I like to think my computer is well organised but often I am liooking for something when I am not quite sure about it - who wrote it? what was it about? how old is it? and more....
BUT we all know "there is no such thing as a free lunch" (see what we know about the history of this expression at https://en.wikipedia.org/wiki/There_ain%27t_no_such_thing_as_a_free_lunch). There is a connection between your private catalogue of your things and the World Wide Web - if you allow for this. There is a default that you need to access and change if you want to keep your activities private - otherwise, next thing, you'll start seeing ads related to what you were doing in your next Google or Facebook feed!
So perhaps you should have a look at the Spotlight preferences - you'll find these by clicking on the HELP button when you use Spotlight - and then you can think about what settings you want for your 'private' cataloguing system.