Use this phrase to announce a decision that is now ready to be shared with the public.

An "official" decision is final. It has been confirmed by someone with authority. For example, if you marry someone, the marriage is "official" when you complete all of your marriage paperwork with the government, or when you complete your wedding ceremony.

Recently, more and more people have started to use "it's official" to talk about things that are only their own personal opinion. For example:

It's official: Burger King is the worst restaurant in the world.