AI Revolution -- Voice Assistants & Their Smartness

Every day, Every Hour, Every Minute, we are saying few simple words like "Hey Google" or "Hey Alexa" or "Hey Siri" to know something or to get our works done. "Hey Google, How do you work?" or "Hey Alexa, Why are you so smart?" or "Hey Siri, What's behind your success?" It's simply because as a client we never bother about these things. In any application clients are the ones who needs to be satisfied and in today's world these assistants are so much smarter that there is no reason to think or ask these things as a client. But as a Tech Enthusiast, or as a guy from CS background it's always too much fascinating to know about behind the scene technologies, these popular companies are using to make these smart assistants capable of extraordinary performance.