Also i sort of wondered why this is nessesary, why can't i just run a loop without doing all this?
So your game runs at the same speed on any PC. Render tweening ensures that the screen is updated at the same rate on every PC, regardless of how fast the game logic is going.Its bad practice to have your game running 20x faster on a new PC than it does on an older system, since it'll be unplayable on one or the other.
I don't see the point trying to code for 60fps, personally. I usually lock it to 30fps. Gives you twice as much processor time to get stuff done, with far less risk of hitting a CPU bottleneck.