Actually, for 12 months they (should) cover everything INCLUDING many wear items like brakes. Just ask some Hellcat owners about getting those expensive front rotors replaced for free because of clicking or squeaking. Some dealers are better than others when it comes to warranty work though. But no dealer is going to replace your bald tires at 5k after you do a massive burnout
So it's basically 12m/12k includes wear items (within reason), 36m/36k bumper to bumper defects, and 60m/60k for powertrain issues.
To answer
@Jako if you have a clunking ball joint in month 38 of your 39 month lease, you have to pay for it. Both because you're out of the 3/36 warranty, and because you are obligated to give the vehicle back to the lease company in good condition (or you can pay their damage fees instead or trade it in). A bad lifter in month 38 would be fixed under warranty though since you'd still have the 5/60 powertrain warranty.