Memcached a free open source which helps website with high efficiency and greatest performance. Memcached is the caching technique which allow your website to load your files much faster. It’s fully object oriented caching system.
Memcached is an in-memory key-value store for small chunks of data from results of database calls, API calls, or page rendering.
Memcached is simple yet powerful. Its simple design promotes quick deployment, ease of development, and solves many problems facing large data caches. Its API is available for most popular languages. Facebook uses this technology to attract users and that results in billion of users visit the site. You can have revenue through Memcached by speeding up the dynamic pages.
Source : http://memcached.org/