Cross-Origin Resource Sharing (CORS) is a security feature that restricts web pages from making requests to a different domain than the one that served the web page. CORS policies are implemented to prevent malicious websites from accessing sensitive data from another domain. However, legitimate cross-origin requests can be allowed by configuring the server to include specific HTTP headers that grant permission. CORS headers include Access-Control-Allow-Origin, Access-Control-Allow-Methods, and Access-Control-Allow-Headers. Proper CORS configuration is essential for enabling secure cross-origin interactions while protecting web applications from security vulnerabilities.