CORS (Cross-Origin Resource Sharing) is a crucial security feature that governs how web browsers interact with resources, such as fonts, images, scripts, or APIs, from different domains. It enables controlled sharing of resources between different origins (domains) to prevent unauthorized access and protect user data. Without CORS, browsers apply the 'same-origin policy' which restricts cross-origin requests for security reasons. With CORS, website owners can specify which domains are allowed to access their resources and what types of requests (e.g., GET, POST) are permitted. CORS relies on the use of special HTTP headers, such as 'Access-Control-Allow-Origin', 'Access-Control-Allow-Methods', and 'Access-Control-Allow-Headers', to communicate and enforce these policies. It is important for developers to understand and implement CORS correctly to ensure secure and reliable communication between web applications.