"Indeed" is more in use in the UK than in the US, generally. "Indeed" and "exactly" can be used to agree or concur but are often used somewhat differently. Generally used for responding with some enthusiasm, to the remarks make by another. "Exactly" can also refer to specific, exact numbers and quantities. "Luxembourg is a small country." - "Indeed (it is)!" "Do you like chocolate?" - "Indeed!" "The service is slow in this cafe." -"Indeed!" "The train arrives at noon?" - "Exactly." "The film was funny, but I would say that it was better for children" - "Exactly." "Let me get this right... you only want 123 ml.?" - "Exactly." "Does that cost exactly the same amount that you earn in a week?" "Certainly", as a response, is more likely to be a response to a YES/NO question or, again, to confirm and agree with emphasis or enthusiasm. - "Would you be willing to come to the theater with me?" - "Certainly!" "It is very cloudy today". - "Yes, it certainly is!" (or "Indeed!") I hope this helps!