A Banyan is a fig that starts its life as an epiphyte (a plant growing on another plant) when its seeds germinate in the cracks and crevices on a host tree (or on structures like buildings and bridges). “Banyan” often refers specifically to the Indian banyan (Ficus benghalensis), which is the national tree of India, though the term has been generalized to include all figs that share a characteristic life cycle. [source]
The seeds of banyans are dispersed by fruit-eating birds. The seeds are small, and most banyans grow in forests, so that a plant germinating from a seed that lands on the ground is unlikely to survive. However, many seeds land on branches and stems of trees or on buildings. When those seeds germinate they send roots down towards the ground, and may envelop part of the host tree or building structure, giving banyans the casual name of “strangler fig”.
The “strangling” growth habit is found in a number of tropical forest species, particularly of the genus Ficus, that compete for light. Any Ficus species showing this habit may be termed a strangler fig. [source]
You can read much more about Banyan trees on Wikipedia. This photo was recently posted to reddit, however a photographer was not listed. I did a reverse image search on Google and TinEye but did not have any luck identifying the original source.