I know you could Google this question. Please tell me you can read. You need a basic biology class. and to pay REAL close attention.
Balls (testicles) store semen that is transferred to the penis and goes into the hand or toilet or girl when the owner of the balls ejaculates.
The urinary tract is involved in passing the pee (urine) from the kidneys to the end of the urinary tract which is in the end of the penis. Yes, pee and semen come out of the same little hole. It is disgusting, but you'll get used to it.
The penis is that long dangly thing that gets hard and long and goes looking for something, hopefully, a vagina to jump around in and then go to sleep in.
Geesh, kids. Please tell me you are not sexually active or at least protecting yourself from dumb-asses. Yes, there are probably boys out there who know less than you and they lie.