Drag and drag page builders allow you to control how your website pages look by simply moving elements within a visual interface. One of the reasons they have become so popular is because they require no technical knowledge to use. Even a novice can create professional looking pages in seconds using a drag and drop builder.
The first page builder I remember testing extensively was Visual Composer in 2011. Developed by WPBakery, I was really impressed with what the plugin could do.
Page builders have become so popular that a large percentage of themes released on ThemeForest come packaged with drag and drop builder plugins so that users can create complex layouts on their own.