[Physicist]

In an electrical insulator, the electrons are not free to move throughout the material. If "electrons" are physical but "electricity" is not, then instead of thinking of a brick wall stopping "cars", think of a brick wall stopping "traffic".

As for thermal insulators and conductors, they are totally different things from electrical insulators and conductors. They work according to different physical principles. A diamond is a lousy electrical conductor, but there is no better thermal conductor.

[XBob]

a barrier is supposed to stop 'everything', an insulator merely stops 'some' things - eg a bullet proof vest is a 'barrier' and an 'insulator', a jacket is an 'inulaotor' but not a 'barrier'.

but in fact, really, nothing is a total barrier or a total insulaor. hydrogen goes through just about anything we use to contain it, eventually leaking out - just measure outside a hydrogen container or special hydrogen hose. cosmic rays go through anything (I think).