What does the phototreceptor do?

Answer 1

If you mean photoreceptors, then they are responsible for detecting light and, therefore, enable us to see. photoreceptors are arranged in certain ways to help us recognize different objects. Some photoreceptors are activated (and thereby sends signals to the brain) when they detect light, while others are activated when they do not detect light. The more light (or darkness) each cell detects, the more active they become.