Coauthoring will allow multiple people to create and edit content within a single SharePoint page at the same time. This bring content creation in SharePoint to have a similar experience to working in other Microsoft Office Apps such as Word, Excel, and Powepoint.
Just like the experience in other Office Apps, when you are editing a section in the SharePoint page, it will become effectively locked down to others that may be in the page. You will see a border around the section in a color that will match the border of the avatar for that person at the top of the page.