The occipital lobe takes up the back portion of the brain. See the image below to find the location of the occipital lobe.
By Anatomography - en:Anatomography (setting page of this image), CC BY-SA 2.1 jp, Link
Vision is the main function of the occipital lobe. The primary visual cortex which is located here interprets visual stimuli and information that comes in through the retinas of the eyes. From the information collected here, the occipital lobe can interpret characteristics of what is being seen such as depth, distance, location and identity.