We visited the oculus and was marveled at the size for it being in the city. My question I quests would be, is what does it have to do with the world trade center.

Is not far from World Trade Centre. The connection is important

The Oculus is a commuters hub connecting trains within the city and to another state. The structure itself has the appearance of a bird's wing in flight, representing FREEDOM....

The train station can be accessed from inside.

They are all one and the train system ran there as well