The dorsal nerve cord is an anatomical feature found in chordate animals, mainly in the subphyla Vertebrata and Cephalochordata, as well as in some hemichordates.
This is an important feature as it distinguishes chordates from other invertebrate phyla such as annelids and arthropods, who have solid nerve cords that are located ventral to the gut tube and often separated into a ladder-like series of segmental ganglia.
All the structures developed from the dorsal nerve cord are covered by meninges and enclosed by the bony (sometimes cartilaginous) axial endoskeleton, namely the cranium (hence a synonym word for vertebrates, the craniates) and the spinal canal.
The hollow cavity inside the neural tube is filled with cerebrospinal fluid (CSF), and further develops into the cerebral ventricles, aqueduct and central canal, which communicate with the also CSF-filled subarachnoid space via the median and lateral apertures.
Other terms such as "anterior", "posterior", "front", "back" and so on are body relative directions that are also often used, sometimes to describe a ventral-dorsal relationship among an organism's structures.