Express is a web application framework for Node.js, released as free and open-source software under the MIT License. It is designed for building web applications and APIs.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
PayPal is an online payments system that supports online money transfers and serves as an electronic alternative to traditional paper methods like checks and money orders.
Ubuntu is a free and open-source operating system on Linux for the enterprise server, desktop, cloud, and IoT.