Belief is an act, it's making a choice to place your confidence or trust in someone or something in the absence of certainty. When I say I believe in God, it means I think that God probably exists because I have confidence in the legitimacy of the philosophical arguments I've heard that support the existence of God. It means I also have confidence in various people I've read on the subject who argued for the existence of God. It means I also have confidence in my own ability to reason. Assenting to a proposition really has many aspects.
When you say you have an idea, or views, or opinions, you aren't necessarily placing confidence in anyone or anything. That's the key difference; belief implies a confidence or trust in certain people, certain arguments, certain books, certain ideas, etc. It involves faith. But to believe or to have faith does not signify that you don't think you could be wrong; on the contrary, to say you believe something implies a lack of certainty. If you were certain, you'd say that you know it's true rather than that you believe it's true.