Internet Explorer has seen several iterations over the past 20 years. IE 11 is the last version of Internet Explorer. Microsoft Edge is the future of web browser which got introduced in Windows 10. Internet Explorer, in the past, was a Software-as-a-Product. Where as Microsoft Edge is a Software-as-a-service and will be continuously updated. IE 11 is recommended for legacy websites that relies on legacy binary extensions, such as ActiveX controls, and legacy CSS concepts, such as CSS expressions. Microsoft Edge is meant for the modern web HTML5/CSS3 etc. Ideally, all websites should be upgraded to the modern web standards but it’s a fact it’s a very resource intensive process. So, while we are upgrading older web sites to support the modern standards, we still have to satisfy customers by letting them use older web sites in a newer version of web browser. That’s where we have to rely on various compatibility options provided by the browser, such as Enterprise Mode, Enterprise Site Discovery etc.
Web Application Compatibility Lab Kit is a primer for the features and techniques used to provide web application compatibility during migration. Download link is available on this webpage: https://technet.microsoft.com/en-us/browser/mt612809.aspx