Try the switches for plane N1, and watch both lists.
Most aircraft carry a transponder that broadcasts ADS-B: its identity, position from satellite navigation, altitude, speed and heading, about twice a second, on 1090 MHz. It isn't encrypted, because it isn't meant to be secret. Air traffic control and other aircraft use it to keep planes apart. In the US and Europe, most aircraft flying in controlled airspace are required to transmit it.
A radio that can hear 1090 MHz costs about as much as a dinner out: a USB dongle and a small antenna. Thousands of hobbyists feed what they receive into sharing networks, such as ADS-B Exchange, OpenSky and the big commercial flight tracking apps. Put enough of those receivers together and you can see almost every plane in the sky. For aircraft that send no position, the networks can still work it out from the tiny differences in when several receivers hear the same signal. That's called multilateration, or MLAT.
The Limiting Aircraft Data Displayed program, run by the US aviation authority, lets owners ask that their aircraft isn't shown in data feeds that come from the authority itself. Services that use that data respect it. But the plane keeps broadcasting, so anyone with their own receiver still hears it. Some sharing networks deliberately don't filter at all.
The Privacy ICAO Address program gives an aircraft a temporary identity code that isn't linked to its owner in the public register, and it can be changed. It makes it harder to say whose plane it is at a glance. It doesn't make the plane invisible: the position is still broadcast, and patterns like the same airports at the same times can give it away.
Not if you want to fly in controlled airspace. The broadcast is how everyone avoids flying into each other. That's the whole reason the data is public, and the reason the ElonJet saga went the way it did.
This page explains the technology with fictional aircraft. It doesn't track or show any real plane.