2. How does a reset switch work ? Does it "cut power" ?
No.
Does it make all the electricity flow away via ground
No.
or something ?
It connects the reset line to ground. The reset line is just a normal logic input to the CPU (and to many of the other ICs on the motherboard).
For a typical 8-bit microcomputer, the reset circuitry looked something like:
-----+----------+------- V+ | | +--o---+ +-+ | Vcc | R | | | | | | | CPU | +-+ | | | | RST o------+-----+ | | | | | | | o | | | C --- |) SW | Gnd | --- o | +--o---+ | | | | | -----+----------+-----+- Gnd
At power-on, the (initially uncharged) capacitor will pull the reset line low. At any time, pressing the reset button will pull it low.
Without a power-on reset circuit, the CPU would just start executing from an undefined state (i.e. undefined values in all registers, including the program counter). Simply cutting power to the CPU doesn't necessarily reset it unless the CPU has a built-in power-on reset circuit (microcontrollers such as the PIC do; CPUs such as the 6502 or Z80 typically didn't).
3. How to connect the reset switch ? Should the brown wire go to GND or vice
> versa ?
It doesn't matter; switches aren't polarised.