This is the 129th most frequent Indonesian word.
yaitu
"Yaitu" means "that is" or "namely."
In this sentence, 'yaitu' introduces an explanation or specification that gives more information about the previously mentioned idea (my new hobby).
Saya memiliki hobi baru, yaitu berkebun.
I have a new hobby, namely gardening.
In this case, 'yaitu' definitionally connects the general statement to a specific instance or elaboration (spicy food being the one type of food he likes).
Dia hanya menyukai satu jenis makanan, yaitu makanan pedas.
He only likes one type of food, which is spicy food.
Here, 'yaitu' is used to introduce a specific elaboration or clarification regarding the previously mentioned subject (something interesting).