Twitter is very powerful platform for keeping your opinion to the world . twitter was made so that celebs, politician, brands, and any other famous personality can get connected to there followers followers can ask anything directly to the famous personality.
twitter also help you get the brief news around the world and you can use it to know whats thing that people are most talking with the help of watching twitter trends,
twitter allows you to tweet in a 140 characters limit . so you have to the point to write anything.
twitter can be helpful in filing a complain like on any product you having problem you can directly tweet to the co. and they will surely reply.