How does a screwdriver tester work?

[ap]

Hi,
Can anyone here may explain to me how does a neon screwdriver tester work?
I know that there should be a current that flows through the neon bulb and
then to a resistor and then through my body. All is quite understandable
while I'm grounded, but why the bulb lights (rather dimly) while I'm not
grounded at all (suppose I'm testing while on a wooden ladder with rubber
feet)??? Does the current flows into me?

Another question: Should it works also with dc?

Thanks, ap