Contact Form 7 is an WordPress plugin which can manage multiple contact forms. The form supports Ajax-powered submitting, CAPTCHA, Akismet spam filtering.
Gravatar is a service for providing globally unique avatars.
Jetpack is a popular WordPress plugin created by Automattic, the people behind WordPress.com.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
WordPress is a free and open-source content management system written in PHP and paired with a MySQL or MariaDB database. Features include a plugin architecture and a template system.
WP Engine is a website hosting provider.