How the Internet works
Goes through your service provider’s network, potentially over some other networks too, to your destination. And then finds a route back again.
When you go online — browse the web, send email, or whatever — you potentially share a lot of information with various companies.
Whoever providers your DNS resolver can tell which sites you are going to, even if not every time your visit. And even though it doesn’t get to see anything of the site content — anything in a URL passed the first forward slash — this can still be very intrusive
Internet access provider knows where it is routing your packets — which IP addresses are your destinations (even if they are not your ultimate destination). For example, the local access network provider (e.g. the operator of the Wi-Fi network to which you are connecting).
It can be very tempting and convenient to connect to a coffee shop's Wi-Fi hotspot (or what you think is their Wi-Fi hotspot).
There are some security considerations to bear in mind.