What is the difference between Behavior flow and User flow?

Behavior flow reports tell you about the behavior of the user on your site. The way he/she navigates from page to page or event to event. The reports can display data according to content grouping, events, automatically grouped pages or both pages & events. You can access the behavior flow reports in google analytics by navigating to Behavior >> Behavior Flow.

Behavior flow reports focus on the content that keeps the user engaging. It also helps you identify the content with most potential issues. 

User flow reports compare volumes of traffic from different sources, showing the different marketing channels that are sending traffic to your site. User flow reports also reveal information about the origin of the users.It shows traffic coming from different countries. In order to access to user flow reports navigate to Audience >> User Flow