Coral is the secretion of coral polyps, the main component is calcium carbonate. It is a marine cylindrical coelenterate, which is automatically fixed on the calcareous bone piles of ancestors corals at the white larval stage.

And sticks to each other in clusters in a dendritic shape, which is what people call coral stones.

The main body of a coral reef is made up of coral polyps. Coral is a kind of coelenterate in the ocean. It feeds on the tiny plankton in the ocean. During the growth process, it can absorb calcium and carbon dioxide in seawater, and then secrete limestone to become its own shell.

Each individual polyp is only the size of a grain of rice. They live together in groups, metabolize, grow and reproduce from generation to generation, while constantly secreting limestone and sticking together.

These limestones are then compacted and petrified to form islands and reefs, so-called coral reefs. Many coral reefs often have large numbers of them attached to the bottom due to their attachment.

Corals are Cnidaria (Anthozoa) marine invertebrates. The body of a coral is composed of two germ layers: the outer cell layer is called the ectoderm; the inner cell layer is called the endoderm. Between the inner and outer germ layers, there is a thin mesodermal layer without cellular structure.

Food enters from the mouth, and food residues are discharged from the mouth. These animals have no head and trunk, no nerve center, only the diffuse nervous system.

When exposed to external stimuli, the entire animal body responds. Its lifestyle is free-floating or anchored to the bottom habitat. Existing coral, living in the ocean.

Not only are coral reef ecosystems biologically rich, they are a source of natural beauty, and they provide countless services to the coastal communities they support.

If a coral reef is degraded or destroyed, the services it once provided will be reduced or eliminated, possibly forever.

Coral reefs provide spawning and nursery grounds where economically important fish populations need to thrive. Coral reefs help protect coastal communities from storm surge and wave erosion, both of which are likely to increase when sea levels rise. Coral reefs provide millions of jobs for local residents through tourism, fishing and recreational activities. Coral reefs are also the "medicine cabinet" of the planet.

Many drugs come from coral reef organisms, including the antiviral drugs Ara-A and AZT and the life-saving anticancer agent Ara-C.

Thousands of other useful compounds may remain undiscovered, however, their discovery depends on the survival of coral reefs. In addition, coral reef ecosystems are important sites of cultural heritage in many parts of the world, and the cultural traditions of millions of people are closely associated with coral reefs.