Combined splash page is when the LOGIN box is on the same page as the other modules (Splash page is the same as the login page).
Your hotspot can work in a combined mode, or you may want to keep the LOGIN section separated from the other parts of splash page, where users can buy access, activate vouchers etc.
Hotspot FREE Basic and Social can only work in combined mode
Open-Mesh and Mikrotik supports the combined mode only
Combined mode has to be set in the Control Center, as well as in the router to make it work