The frontend is what people see. The backend is what makes it real: user accounts, saved data, files, emails, payments. Lovable can build both, but if you only prompt for screens you will end up with an interface that pretends to work.

Before you ask for a new feature, state what must live in the database and who owns the data. A screen that shows your orders needs an orders table, a logged-in user, and a rule that only that user can see them.