Tropisms are the curving or turning movement responses that occur in response to directional stimulus. Plants alter their growth so that they may grow in more favorable conditions. There are different types of tropisms such as: phototropism, gravitropism, thigmotropism, hydrotropism, and heliotropism. I believe that this tree is growing towards the light because to the left of it there is a building and a taller tree (not pictured) that blocks some of its light. The tree then manages to curve to a brighter area for light.