Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Razorpay is a provider of an online payment gateway that allows businesses to accept, process, and disburse payments.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.
Ubuntu is a free and open-source operating system on Linux for the enterprise server, desktop, cloud, and IoT.