The phrase "main homescreen" refers to the main or primary screen on a device where you can see all your apps and widgets. It is the first screen you typically see when you unlock your smartphone or tablet. Full definition
An advertisement is displayed on the standby screen and at the bottom of your main homescreen. (goodereader.com)
Samsung's Hub widgets are plastered on the main homescreen including S Suggest which is an app recommendation service that has been revamped to and now break apps into categories. (t3.com)
It seems as though the N button now brings you to the main homescreen and that the navigation elements are always visible. (goodereader.com)