It is the pop-up keyboard necessary to type on tablets without a real keyboard.
Under Settings > Preferences you will find the option ’’Show virtual keyboard’’. This option only exists on the Windows version of the Mobile Control app*. For tablets without a physical keyboard: Please do not switch off the virtual keyboard. Switching it off leads to a deactivation of the pop-up keyboard for your tablet in general, not just for the mobile control. For PCs and laptops with a real keyboard: It is advisable to switch off the virtual keyboard. The virtual keyboard is not necessary for typing, if a real keyboard is present. Furthermore, on PCs with real keyboard activation of the virtual keyboard leads to having to click on all buttons twice to get a reaction.
*) Current Mobile Control versions don't support Android tablets anymore, but Windows tablets exclusively.