Why do websites use Nginx instead of Apache?

Nginx is providing fast, more security, memory caching, scalable flexibility and more fine tuning options. This will be helpful for million request websites comparing to Apache. Mostly, million request websites facing unavailability or slowness issue at peak hours because of load balancing but nginx will handle more request with fine tuned configuration.

I think apache used widely but now we are facing c10k problem ( concurrent100000 request ) so researcher develope new Architecture thats nginx. It provide more scalability over apache webserver If u need more in details just email me