how does movement work in unity code example

Example: how to make movement in unity in c#

public Rigibody rb;
public float _write_your_speed_x;
public float _write_your_speed_in_y;
public float write_your_speed_in_z;

void Update(){
  if(input.GetKey(keycode.Uparrow)
  	trasform.position += new vector3(_write_your_speed_in_x,_write_your_speed_in_y,write_your_speed_in_z);
  else 
     transform.position += new vector.zero;
}