Can someone please explain to me why the parametric coordinates can only represent one branch of the rectangular hyperbola with the equation , and what would the parametric coordinates of the other branch be?

I'm stuck on a question relating to the rectangular hyperbola, which is:

The normal at , where t>0, passes through the point . Find the non-zero value of t, giving your answer as a natural logarithm.

I must admit I have absolutely no idea how to even begin the question. Can someone please enlighten me?