If we look at their Wikipedia page, If This Then That, also known as IFTTT, is a free web-based service to create chains of simple conditional statements, called applet. An applet is triggered by changes that occur within other web services such as Gmail, Facebook, Telegram, Instagram, or Pinterest. For example, an applet may send an e-mail message if the user tweets using a hashtag, or copy a photo on Facebook to a user's archive if someone tags a user in a photo.
As you might have noticed, applets are the heart of IFTTT, it's the result of your application. Thanks to it, you will be able to create almost anything you want or need. All the big techs firms are on this platform and share their services such as Google, Facebook, Philips and many more.