SP pagebuilder developed by JoomShaper guys. SP Page Builder is a most flexible Drag & Drop page builder For Joomla 3.x. You can create any layout you want, instead of template that lock you into pre-created layouts. It can be used for constructing unique-looking Pages. It can be used wit any template, free or commercial. It allows you to easily add created page(s) in menu and display with useful and cool effects inside. Whether you’re a beginner, web designer or developer building commercial sites for clients or a business owner managing and maintaining your own website. SP Builder’s flexibility and functionality means one thing: web content design made easy. Take full control over your Joomla! 3.4+ site with SP page builder extension.

The offical documentation can be found here