Nobody seems to have mentioned Holes. Holes are positive charge-carriers. Yeah - they're virtual, they're not like positrons or protons. But they behave just like electrons going "the other way".

My understanding is that a hole represents the absence of an electron. If an electron is removed (e.g. by rubbing), there's remains a physical object bearing a positive charge: the proton that was originally associated with that electron.

I haven't heard anyone talking about holes for years. Are they now deemed an outmoded concept?

[Edit: should have read further down the comments :-)]