Battery gauge - Tells you how many volts are being supplied by the alternator to the overall system. Anything over 14 and you are operating normally. Below that could be a sign of an issue. It looks like your Runner is off so its impossible to tell if it's working properly.
Gear Shift - put the vehicle in D and drive around. Pushing it to the left form D will allow you to pick the gear manually. For most people this feature is not needed and will never be used.
4WD - You have a Limited, which means that your vehicle is always in 4WD. Turing the 4WD selector one turn, will lock the front and rear drive shafts together, meaning that you will always have 50% power going to the front and the rear equally. Turing one more form there (you will have to press down a button on the selector to engage this mode) will engage 4WD Low. This will use a different set of gearing giving you much more torque, but you will go much slower. Considering that you don't understand these features, don't use them. Incorrect use of either could cause massive damage to your drivetrain. They are meant for off road situations and should only be used when needed.
SOS Button - This will allow you to connect to roadside assistance in the case of an emergency. This is a subscription service and you have to pay for it to work. I'm assuming you bought your Runner used so this will likely be deactivated. It can be reactivated if you wish (for a subscription fee) .