What is system 1 and system 2 in simplified terms?

System 1 - operates automatically and quickly, with little or no effort and no sense of voluntary control. It is very impulsed thinking that usually comes from memory.
System 2 - Allocates attention to the effortful mental activities that demand it, including complex computations. It requires effortful activities.
Do you have a more simplified way of explaining this? I'll be glad to hear this out.