It's not just "the simplest interface", it's the de-facto application/web page for playing Chess. You'll find grandmasters like Magnus Carlsen and Hikaru Nakamu

It's not just "the simplest interface", it's the de-facto application/web page for playing Chess. You'll find grandmasters like Magnus Carlsen and Hikaru Nakamura playing there. You can access their games and every game ever played on the website. You can track your performance, analyze your games, train with puzzles, play against various bots, etc.