Coral reefs are complex marine ecosystems that support diverse marine life. They are formed by **coral polyps**, tiny organisms that secrete calcium carbonate to build reef structures. These reefs provide habitat and shelter for various species, including fish, invertebrates, and algae. The **symbiotic relationship** between coral polyps and **zooxanthellae** algae is crucial for reef health; algae provide nutrients through photosynthesis, while corals offer a protected environment. Reefs also protect coastlines from erosion and support local economies through tourism and fishing. However, they face threats from **climate change**, **ocean acidification**, and **pollution**, making conservation efforts essential for their survival.