Other than the fact that EFB must be installed with appropiate charts and other manuals, is there any difference between EFB and normal tablet? Can I use the same tablet I play Plant VS Zombie as EFB if I load appropiate charts?
The FAA (unsurprisingly) has definitions of different types of Electronic Flight Bag (EFB) systems, which you can find in AC 120-76C. It's targeted at airlines, but the concepts are generally applicable.
They break them down into Class 1, Class 2, and Class 3 EFBs, and the answer is a little different for the different classes:
Class 1 EFB Hardware.
This is what most of us General Aviation Folks use: A portable computer or tablet considered "portable electronic devices" with no specific FAA approvals.
Per the FAA a Class 1 EFB can't be "mounted to the aircraft" or connected to the aircraft systems or a dedicated power supply (i.e. they can't be permanently wired into anything), but you can plug them in to an "existing aircraft power supply" (like the cigarette lighter port) for battery recharging.
This is what most of us GA folks are using - an iPad with Foreflight and Stratus is technically a "Class 1 EFB".
This is just a regular computer, so it can in fact be the same device you play Plants vs Zombies on (though if you're using it in an airline environment they've probably locked it down and restricted what you can do: Plants vs Zombies is probably not available in the cockpit of your Southwest flight).
Class 2 EFB Hardware.
Class 2 EFBs are essentially Class 1 EFBs that get mounted to the aircraft, but can be easily removed by the flight crew (for example a GPS or iPad in a panel-mounted cradle) and may connect to aircraft data systems via cables or wireless connections (for example Garmin's Flightstream system).
Class 2 EFBs have the same battery-charging provision as Class 1 EFBs, but can't be directly wired into aircraft power. As far as the FAA is concerned they're still "portable electronic devices".
This is what the more advanced bits of GA are using - An iPad with Garmin Pilot communicating with your GTN stack via flightstream to get its GPS position & transfer flight plans.
Again this can be the same device you play Plants vs Zombies on, but the operator may have locked it down to keep their crews from flying past their destination while playing with their laptops.
Class 3 EFB Hardware.
Class 3 EFBs are installed systems with FAA approvals (for type-certificated aircraft).
The chart data stored on e.g. a GTN650 or GMX200 with charts and plates loaded on it would qualify here, as would flight management systems on larger aircraft.
Generally you won't be playing Plants vs Zombies on Class 3 EFB hardware because the approvals for it wouldn't include that capability.
The exception here is the Experimental Aircraft community: Such aircraft may have a consumer tablet installed in the panel and wired into ship's power in such a way as to qualify for all practical purposes as a "Class 3 EFB", and it's possible you could play Plants vs Zombies on your installed iPad in such an aircraft.
Our airline uses second and third generation iPads with CAA approved applications, cockpit mounts(holders) and chargers.
Basically, this combination of iPad(tablet)+software+equipment is EFB.
If AppStore would't be locked you could install and play PvZ.
Heres you can find some material about EFB: