I think bitcoin is a world currency not a private currency and because he does not hold by the government and does not have tax.. and i am agreed for this currency. so all people are wrong tell us bitcoin is a private currency.
Privately that you mean is not bitcoin used or regulated by one government or one company. But privately that is meant by bitcoin you can use freely without a government that will regulate all the systems in bitcoin. Even with a decentralized system all users can make an invasion related to bitcoin so that bitcoin can be accepted by many people.