1. Ought to has a similar meaning to should. They both express the conditional: in other words, they refer to a recommended future action. Ex :
A. You ought to pay him back shortly. You should pay him back in the near future.
B. You ought not (to) speak with your mouth full. You should not speak with your mouth full.

2. Used less frequently than should, ought is always followed by a verb in the infinitive with to, except in the negative form, where we don't need to add to:
Ex : You ought not (to) ask so many questions. It would be better if you didn't ask so many questions.