Why do I see different words in the app than in the help?
The app adapts its words to what you do: as a fitness trainer you see students, classes or sessions, and passes; if you teach, students, lessons and lesson packages; in other professions (coaching or massage, for example), clients, sessions and packages. The help uses the Fitness words everywhere, so if your label is different, it's the same screen.
You can change your profession under Settings → Profile & account → Profession. Only the labels change (notifications included), while your data, the text of message templates you already saved and the template field names stay as they are.