Hangouts is an instant messaging application developed by Google. This application allows you to call any of your contacts on Google.
Built for various platforms, Hangouts is an application you'll want to use if you're someone who keeps hopping from their computer to their Android phone. Google ensures this by making sure you don't get spammed with notifications on a different device like if you were already on a call with someone using Hangouts on your phone.
Speaking of calls, Hangouts is flexible for all types of situations as you can create voice and video calls between individuals or an entire group of people. The only concern about all of this is that Google is constantly taking data to "improve" Hangouts so think about using Hangouts if you'd like to keep your privacy.
Overall, Hangouts is a neat instant messaging application if you are already in the Google ecosystem and aren't too concerned about the company taking some of your data.