Atheists; Why do you think Evolution is a fact, or it disproves Creationism?

Evolution disproves the thought that all animals on Earth were just willed into existence 6,000 years ago. The thought that all life slowly changed over hundreds of millions of years cannot go hand in hand with "God made 'em all the way they are now". Evolution is a theory, just like cell theory, germ theory, or the theory of gravity. Theory is the highest level a hypothesis can achieve. A fact describes an event that happens. A theory explains a law, or a fact, happens. How much about evolution, or science in general, do you actually know?