What are spiracles?

Hint: Insects are the largest most diverse group of animals on earth. They are found crawling over many different places and environments present on the surface of the earth. These insects have many systems that help them to survive and one of these systems is known as the respiratory system.

Complete answer:
Insects are comparatively quite small organisms that are found all over the earth. These organisms have a respiratory system that they use to get oxygen from the atmosphere. The respiratory system makes use of various small organs on the body of the insect that are known as spiracles.
Spiracles are small circular structures that are located on the underside of the insect. These parts are usually located under the dermal plates that cover the underside of the insect's body. They help to take in oxygen from the air around the insect and put it into the hemolymph of the body. This hemolymph contains blood cells that take the oxygen directly to the parts of the body where they can be used to make energy.
Unlike mammals, insects do not need a ton of oxygen and thus these spiracles help the insects to get a sufficient amount of oxygen. However larger more complex animals need to use lungs.

Note:
The spiracles are the respiratory organs of the insect's body system. These spiracles are circular structures that are located on the underside of the insect's body. They help the insect to take in oxygen from the atmosphere.