* Бабушка (Babushka): This is the most common and general term for grandmother. You would use this when talking to her or about her in a neutral context.
* Бабуля (Babulya): This is a more affectionate and informal term for grandmother. You would use this when talking to her or about her in a familiar or loving way.
So, you can use either "Бабушка" or "Бабуля" depending on the context and your relationship with the grandmother.