When something is absolute, it's total and complete. When something is absolutely the case, it's going to be that way — no ifs, ands, or buts.
When you want to be certain that there is no doubt about what you mean, then you say that it's absolutely that way. For example, there is absolutely nothing you can do that will make George Clooney invite you to his house on Lake Como. The moon is absolutely not made of green cheese. When I said that I would absolutely not go to that wedding, I wasn't kidding, and I didn't go. Absolutely can also be an interjection, a statement of emotion, as in, "Am I sure I'm up to it? Absolutely!"