Why is my heat not getting hot?

What is your question?

ive read online a little that it could be a heater core issue, which I'm really hoping that its not, but i also have read that it could be a thermostat issue as well. the air comes out strong and works on every setting. but it never gets warm. so i know its not the blower motor or the resister. i was just hoping that someone could give me a little insight on what the problem may be. I haven't had a chance to really trouble shoot it, but if anybody has and tips or tricks to help me better figure this issue out, it would be greatly appreciated.