whats a -10db pad for? -i dont get it

I think it makes the mic attenuate whatever is coming into it by 10 db. If you leave it at normal, the mic might overload. By switching in the 10 db pad, it means you can go loud, without the mic overloading like it would do at normal.
Or something like that.
I'll use the vintage AKG 451's I had as an example to explain how and when I used the pad. The 451 is a good mic on acoustic instruments and also really nice on hi-hat. The mic didn't have a pad switch but had a screw on module that went between the body and capsule. Recording hi-hat could overload the fet circuit in the body. The pad would reduce the level going from the capsule to the amplifier in the body. The pad switch does the same thing. So, think of the pad switch on many mics as a level control for loud sources. Let your ears and input meter be your guide. If you incoming level is so hot that you've got the pre turned way down, try the pad.
The active electronics in a condenser mic can be overdriven by loud sources. The pad reduces their sensitivity to prevent that from happening. Dynamic mics generally don't have that problem.
They made the microphone with a high output level to get low noise at low sound levels. With high sound levels, you could need to lower the output signal.
There are several considerations here and some design choices.

As stated, one reason for attenuation is to stop the capsule overloading the impedance converter electronics and is usually done by interposing a capacitive attenuator between capsule and FET input.
Another reason is because capacitor mics generally have a high sensitivity, especially LDCs typically 10X, 20dB hotter than the average dynamic. Most budget mixers and AIs don't have their own input pads these days and so the mic could easily overload some AIs even with a loud singer. Some budget mics do this by cutting the output level but an input, capsule pad is vastly to be preferred.