Adaptation is a reversible process. Appearance and/or function are changed in respons to environmental changes. The aim is to improve survival, or (more generally spoken) function. If the process of adaptation itself is improved that is it goes faster, less imprecise, and less resource consuming, then we call that process evolution.
The currently prevailing theory of natural selection is mostly concerned with genetic adaptation. By that misuse the borders between the terms evolution and adaptation are blurred.
