hi mowgli
check this site : ww*w.sensors*mag.*com
you can search for isolation and find many articles about isolation.
galvanic isolation is done by 4 method:
1: optocouplet
2: magnetic (transformer based)
3: capacitive isolation(see burrb*rown isolation products from TI)
4: magneto resistive couplers
galvanic means that there is no ohmic or conductive relation between two part of a circuit data and power and signals is tranfered by non lectrical methods like as optic,magnetic and ...
there is not connection between two part.
bye