Ingonimania i was watching a docu about Bali on my laptop
Here's a situation:
I log into Instagram, Facebook, or WhatsApp on my laptop. A cookie gets save in my web browser that this is Johnny short stack. I then read my news and browse the web. So many websites have a "share on [social media]" button or they have 1 pixel in the webpage which runs code. They see the cookie says johnny and I am at Bali page.
If you installed an app on your computer for whatever, this is even easier and you can be tracked doing anything on the pc.
Same with smart TV, firestick, etc. You have to log in.