The movement of plants towards light is called 'phototropism'.
'Photo' means light, where as tropism means 'to move'
Plants grow by plant cells getting longer, or splitting into new cells.
The cells on the side away from the light grow much faster than those on the sunlight side. This causes the plant stems to bend towards the light.
Phototropism allows the plant leaves to get the full benefit of the sunlight energy.
