Twilio is a cloud communication platform that allows users to make and receive phone calls, send SMS messages, and more. A TwiML bin is a serverless developer environment that enables the creation of custom call flows. In this tutorial, Kyle Kelly-Yahner, a writer for Twitter, Facebook, and LinkedIn, shares a hack to create an apartment buzzer using Twilio and TwiML bins, allowing users to receive calls on their cell phone without needing to set up a server or keys. The solution involves signing up for a free Twilio account, buying a local area code number, creating a new TwiML bin, and configuring it to forward incoming calls to the user's cell phone.