Each page on your site can have its own set of "page elements" under a node that is created automatically for that purpose. Since this site is powered by Bootstrap, each "page element" is essentially rendered as a "row", with its own settings and content.
You can add as many "page elements" as you like on any site page and order them as needed.
There is a special "page element" which is called a "Placeholder". Together with the "Reusable Elements" section under "Site Configuration" you can define page elements that can appear in multiple pages (but you'll have to edit them only once). The Placeholder element features a picker which allows you to choose your reusable element.