Sidefari uses the Safari View Controller to give you access to Safari inside other apps — complete with access to features like content blockers.
In iOS 10:
Sidefari features an extension called "Open Modally in Safari" that will enable you to bring a Safari-based window inside of other apps that enable ways to share website URLs. Why would you want to do this? Perhaps you prefer the convenience of having some Safari features inside the same app, or if you're conscious about your privacy perhaps you don't want to use the custom web browser many apps have.
** Please note that in order for Sidefari to work in iOS 10, you need version 10.2 or greater.
In iOS 9:
When on an iPad, besides the "Open Modally in Safari" extension mentioned above, Sidefari shows as an extra Safari-based browser on the side of your screen thanks to multi-tasking. Now you'll be able to have two websites simultaneously on the same screen.
** Please note that compatible iPads include the iPad Air 2, iPad mini 4, and iPad Pro.