What is precaval and post postcaval vein?

Hint: precaval and postcaval veins are present in terrestrial vertebrates. They are found in vena cava.

Complete answer:
The word venae is derived from a Latin word which means "hollow veins" and cavus means hollow. These are two large veins that collect the deoxygenated blood from the organs and pass it to the heart.
In humans there are two types of vena cava which are described here-
Superior vena cava also called as precaval vein
inferior vena cava also called as postcaval vein.
Superior vein or precaval vein is above the heart that has a diameter of 24nm and receives the deoxygenated blood from the upper half of the body above the alphagram. It is located in the anterior right. Receives blood from upper limb, eye and neck.
Inferior vein or postcaval vein carries the deoxygenated blood from the lower half of the body and middle part of the body to the atrium.

Note:
The superior vena cava and inferior vena cava are together known as vena cava. The system circulation involves vena cava and aorta. These veins return deoxygenated blood from the body into the heart, emptying it into the right atrium.