Gautam Buddha received enlightenment under a Bodhi (aka Peepal) tree in Gaya. During the reign of Emperor Ashoka, a graft branch was sent to Srilanka. While the original Bodhi tree in Gaya withered away after a long life, the branch sent to Srilanka became a long living tree in its own right and continues to live. This tree here is from a graft branch of that tree in Srilanka. So in a way, this is the grandchild of the original Bodhi tree under which the Buddha received enlightenment. It has immense historical and spiritual significance!