Microevolution- this is when organisms adapt to the changing conditions of the environment. It improves existing genes. It does not create new genes. An example that illustrates this is the classic peppered moth arguments. Basically, when the trees are white, there are more white moths, conversely when the trees were turned black by pollution at the turn of the century, more black moths survived simply from being harder to see, not changing into a different moth. The moths are still moths, not a new creature.

Macroevolution-the changes within species that results in a new and separate species. An example of this would be a fish evolving into a bird. This has never been proven or observed in nature.