Welcome aboard and welcome to the wonderful world of electric flight...

If the type of battery you are asking about is a Lipo, then there are probably 2 leads and plugs coming out of it.
The red and black wires with the large plug supplies the main battery power to the ESC and can also be used to charge the battery.
The smaller wires and plug are used to charge and balance the battery.
If a battery is made up of more than one cell each cell needs to be at the same potential as the others. It's like having 2 or 3 glasses of water side by side and having the water level the same in all the glasses.
Balancing is how this is done.
There are 2 ways to balance a battery.

1) Balance the battery after it's been charged. This is like putting a tube between the glasses of water and have the water from the higher level drain into the glass with the lower level. The problem with this is that after all the cells are balanced the battery is no longer fully charged.

2) Balance the battery as it's being charged. This is like having the tubes running between the glasses, but you will also be filling the glasses up with water at the same time. As the glasses fill the water equalizes itself among the glasses until all the glasses are full. Then you turn off the water, or in case of the battery, it stops charging.

Battery chargers come with and without balancing capabilities. If you have a charger without balancing, you should get a balancer to do the job. This is equal to 1) above.

If the charger comes with balancing capabilities then you just plug the small plug into the charger and the charger does the rest. This is like 2) above.

As for needing any kind of switch, you really don't. The ESC has a sort of switch built into it.
The normal startup procedure for an electric plane is to:
1) Turn on the transmitter.
2) Make sure the throttle lever is all the way down (off).
3) Plug the flight battery into the ESC. You should hear some startup beeps as the ESC arms. Some ESCs require you to move the throttle lever all the way up and then all the way down to arm, some don't.
4) Now the plane is armed and ready to fly.