This documentation is not using the current rendering mechanism and is probably outdated. The extension maintainer should switch to the new system. Details on how to use the rendering mechanism can be found here.
The extension implements a memcached backend for the caching framework. As the memcache-PHP-module isn't supported by PHP7 this backend uses the PHP-module memcached instead. It's a backport of the TYPO3 8.7 memcached backend for TYPO3 7.6.
Memcached is a free and open source, high-performance, distributed memory object caching system. To learn more about Memcached, go to http://memcached.org .