Can you smart folks explain some things about IP addresses for me?

[CloudWatcher]

9. detecting / using

Everyone that uses the internet is using IP addresses to communicate. It's no different than putting an address on an envelope to send postal mail, or getting an address from your post office to receive mail.

Many internet services don't bother recording the addresses of their customers. Some do to try and protect against account abuse (e.g. if your login name & password were stolen).

It's often considered semi-private data. E.g. if you have the IP address that someone on Facebook last used to login, then you could make progress in tracking them down in real life. There are services that will tell you the approximate geographical location of any IP address. These geo-location services are not terribly reliable, often getting you to the nearest large city instead of a real address. And they can be defeated by VPN (virtual private network) services. When using a VPN service, you appear to the rest of the internet as coming "from" the VPN and only the VPN and you know otherwise. I.e. they are used as a relay for your traffic and your real source IP address is (in theory) not shared.