HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Kakao platform provides various services such as Kakao Talk, Kakao Talk Channel, Kakao Story as well as Kakao Pay, Kakao Commerce, Kakao Page provided by the subsidiaries. Users can use all Kakao platform services with a united account called Kakao Account.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
PHP is a general-purpose scripting language used for web development.