Developer mode summary:

• PHP stack traces are shown in the browser
• XML files are validated againts their schemes
• Static assets are created on the fly
• X-Magento-* debug headers are added to responses
• Debug logging can be enabled
• Static asset minification and bundling not applied

 

Production mode summary:

• Static assets are not created on the fly (unless configured static_content_on_demand_in_production => 1 )
• PHP Stack traces are hidden
• XML files with errors are silently ignored
• Caching can not be disabled in the admin
• Debug loggin is always disabled
• Developer section of Stores -> COnfiguration -> Advanced is hidden