Voice Intonation is a variation in spoken pitch which is used to express a range of different emotions and attitudes of the speaker. So by changing the pitch we affect the meaning of communication.

Saying the same word (or words) but with a different intonation could imply or suggest very different meanings such as;
curiosity, anger, love, boredom, appreciation, discomfort, sarcastic, surprise, shock, disbelief, joy, interest, not happy, interrogation, sad, nervous, frightened etc.