What are coral reefs?

Coral reefs are large underwater structures made up of tiny, living organisms called corals. These reefs are formed by the skeletons of corals, which build up over thousands of years. Coral reefs are found in warm, shallow waters of the oceans, and they are home to a wide variety of marine life, including fish, plants, and other sea creatures. Coral reefs are often referred to as the “rainforests of the sea” due to their rich biodiversity. They provide essential services, such as protecting coastlines from erosion and supporting fishing industries. However, coral reefs are threatened by pollution, climate change, and overfishing.

This question related to Chapter 2 Social Science Class 6th NCERT.
From the Chapter 2. Oceans and Continents.
Give answer according to your understanding.