In order to home or migrate, animals need a system of navigation. Some of these are outlined below.
The earth has it's own weak magnetic field. Some animals have magnetite crystals in their brains that are able to orientate to this field like a compass needle. The net result of this is that they are always able to find north and orientate themselves towards a fixed point.
Some birds have crystals so sensitive that they are able to detect magnetic abnormalities due to features such as mountains, helping with micro-navigation
Light arriving from the sun has a certain polarisation, a characteristic of light that is directional. By polarising their sight, birds are able to see a bright patch in their vision and therefore orientate themselves to the sun
Many animals also use the sight of the sun to orientate themselves, such as bees.