These are pretty much like your headphone wiring.
The tip has 3 contacts (much like a headphone too or headset of a cellphone).
There is just a main ground and 2 other wires.
If the common ground and one wire is connected, the focus is tripped.
When the other wire is connected to the common ground again, the shutter is tripped to take the picture.
If that connection is held for a long time (has a push lock) the bulb function is activated 'coz so long as the connection is not severed or disconnected (locked) the shutter remains open for night or long time exposure shooting.
THis is how simple these devices are.
We even have a thread here at the forum as to how to make one if you want to make your own.
The jack/tip used for this is the one commonly used for the headset of a cellphone (like a small stereo headset jack).