Distinguishing Between Void and Voidable Contracts

Brother, I really need your help here. I've been struggling to understand the difference between void and voidable contracts. According to Section 2(h) of the Indian Contract Act, 1872, a contract is void if it is not enforceable by law. But then, Section 2(i) says a contract is voidable at the option of one of the parties if certain conditions are not fulfilled. Dono mein kya fark hai exactly? Can someone explain it in simple terms? How is a void contract different from a voidable contract? I've gone through the Act three times, but I still can't figure it out. Help a brother out! TS LAWCET exam is coming soon, and I want to get this right.