"Mum, what's the meaning of Gerbang Laut terbentuk apabila hakisan ombak berterusan secara bertentangan di antara dua buah gua di sebuah tanjung."
Google translate turned up the following:
Hmm... I think I need pictures.
Finally, I found this and was able to show and explain it to her. They say a picture says a thousand words. It really does. The following slides gives a very good explanation of Geografi Tingkatan 1 Unit 6, Bentuk Mukabumi Pinggir Laut. Thanks to the person who created it.