Can someone explain oiuja boards to me?

Yes - they're either a bit of cardboard with printing on it or a homemade job consists of bits of paper with the alphabet, numbers 1-10 and the words 'yes' and 'no' written on them spaced roughly in a circle around which people sit and put the fingers on either a thing called a 'planchette' or an upturned wineglass. Dubious questions are then asked - intended for the dead - and someone on the table then unconsciously pushes or pulls on the glass so that it moves around to the various letters etc to spell out "answers" all of which are purely coincidental and usually quite wrong leading to all sorts of silly things which then occur being but down to the board instead of to sheer chance and coincidence. Needless to say, the people doing the pulling/pushing always deny all knowledge of so doing.