If you are hopeful, you are fairly confident that something that you want to happen will happen.

If something such as a sign or event is hopeful, it makes you feel that what you want to happen will happen.

A hopeful action is one that you do in the hope that you will get what you want to get.

If you refer to someone as a hopeful, you mean that they are hoping and trying to achieve success in a particular career, election, or competition.