What is transform.forward?

I am working with a project getting help from a tutorial where he used transform.forward function.He didn’t explain this function.So I need help.

transform.Forward is a Vector3 that tells you where the object is pointing at.

I think that setting it triggers another function like orthonormalization. But I can be wrong. I’m also interested in this.

hi;
for example when u want to give force to move to an object u have to mention which direction this force should be applied and forward is one of them;

we have these Directions:
forward , Right , left , up , down

u can multiply any of these direction like this :

GetComponent<RigidBody>().AddForce(Vector3.Forward * 10 ) ;