A categorisation of folk or traditional music played wholly or partially with electric Instruments (Electric Guitar, Keyboard, Synthesiser etc) or modified electric or semi-acoustic instruments (solid bodied mandolin, Bouzouki etc). Simply amplifying acoustic music through a PA System doesn't count.
Sometimes a more gentile term for Folk Rock but actually Folk Rock is a part of the wider field which includes at the extremes Acid Croft , Hypnofolkodelica and Thrash Ceilidh. There is also a recognised Folk Punk movement.
Some extremely good examples of Electric Folk include:
Although to be fair, Tiger Moth did unspeakably good things with harmless lumpy English tunes and all sorts of rhythms.
Examples of British Folk Rock Artists:
Also gave rise to Celtic Rock: