What does the term adaption mean? how does adaption explain the patterns of distribution of plant and animal species in the world?

Adaptation is a phenomenon that is about adjusting certain features to environmental conditions. Ie. birds are adapted to flight as they possess wings, very efficient lungs etc. or tropical plants are adapted to high temperature and humidity as they modified their photosynthesis process. but if some creature is adapted to the specific habitat or conditions, it is hard for it to manage in another habitat/different conditions. ie. birds are fast in the air but on the ground they are quite weak and prone to predators' attacks.