Phalcon is an open source, full stack framework for PHP written as a C-extension, optimized for high performance. Phalcon also is loosely coupled, allowing you to use its objects as glue components based on the needs of your application. Phalcon is a high-performance web application framework for PHP based on the model–view–controller (MVC) pattern. Phalcon is implemented as an extension written in C in order to optimize performance. This is intended to boost execution speed and reduce resource usage with the goal of handling more requests per second than comparable frameworks written primarily in PHP. Phalcon is available on Microsoft Windows, GNU/Linux, and Mac OS X. You can either download a binary package for the system of your choice or build it from source.
Phalcon is a full-stack framework. It promotes the MVC architecture and offers features like an ORM, a Request object library, a templating engine, caching, pagination. Phalcon offers the classic features of a modern PHP MVC-framework so it should be comfortable to use, so in that sense it is just another PHP framework. But where it really stands out from the others is its speed. It is compiled directly to C extension is reason why the framework code dont have to be compiled to C again (because php is interpreting to C). So you are saving a lot of memory a processing time used for framework code.