Here's a breakdown:

* Tetrapyrrole: This refers to the basic structure of the molecule, which consists of four pyrrole rings linked together.

* Pigment: This means it absorbs and reflects light, giving plants their green color.

Chlorophyll is specifically a chlorin pigment, meaning it has a slightly modified porphyrin ring structure (the same type found in heme, the iron-containing molecule in hemoglobin).