What is the node of rotateVetor used for?
I can not figure out in what situations it will be used.

For eg when you aim at point A and you want to change aim to point B. Or when you want aim 45degress to the right side, you get forward vector then rotate it 45deg, you have now direction for 45 deg to the right.

Do not worry rotating vectors will come and tell you (or rather kick hard in rear parts) when they decide its time for them to be used. You will get there.