Good questions. Playing to tracks means that you’re hearing the pre-recorded music in your earbuds. If the entire band is tracked, then no one is actually playing live–only acting. Even the cymbals are dummy cymbals that look to react realistically but make no noise.
There are times when some things are tracked and some instruments or singers are singing live, then they’re mixed together at broadcast time. Typically the award shows feature tracked bands (band is faking) but the singer or singers are actually singing. In the case of something like the Super Bowl where there can be no mistakes and set changes happen so fast, everything is tracked. You’ll sometimes see the singer say something into the mic to the crowd that you can tell is real and it’s audible. What happens is that those are rehearsed. They’re thrown in there to create realism. The audio engineer knows to turn on their mic during those times, then turn it back off when the singing comes back in.