We've all heard of the industrial revolution, right?

Well, according to Jim Cramer, we're in the fourth industrial revolution.

If you don't know what that means, don't panic. 

Basically, Cramer explained, it's the emergence of cloud-based technology. It's the fourth major industrial revolution that has disrupted the world. 

Companies such as Amazon's (AMZN - Get Report) web services, Salesforce (CRM - Get Report) , and Apple (AAPL - Get Report) are just a couple of examples of major companies using the cloud.

All three companies are part of Jim Cramer's Action Alerts Plus portfolio.

Cramer said that he's constantly keeping an eye on various cloud companies and explained that he frequently makes trips out to California to visit Silicon Valley and see where the technology advances are heading.

Most recently, Cramer was in California to cover Dreamforce, which is Salesforce's yearly conference