Of course, Parker Bros didn't invent the Ouija board. 'Modern Spiritualism' kinda did most of the work, and Parker Bros just slapped their brand name on it.
If you need me to explain the concept, here it is: you use a planchette (a small triangular piece of wood or cardboard, generally with a hole in the top) to receive messages from THE OTHER SIDE. You move it around on a cardboard (or wood) board with letters and numbers on it, sometimes even the words 'hello' and 'good-bye' scrolled at the upper left and right-hand corner. There's also a 'yes' and 'no' somewhere on there, just for those of us who are too impatient to let the word spell itself out.
I can't confirm whether it does or doesn't exist. There's questionable evidence on both sides. If you're in a group of people who really commit, and refuse to move the planchette, but just let it 'move', you may have some tedious fun. Usually, though, the case is that there's some joker in the group who either can't wait or wants to mess with everyone else by pushing it to their own answers.
The Ouija Board has been around so long, and been so popular throughout the years, that there are a thousand different incarnations, whether Parker Brothers or not. They range from the cheap and tacky to the incredibly ornate and gorgeous, as well as everything in-between. My personal favorite is a miniature one that came with my precious dvd 'Witchboard'. Heck, you can even use the cover itself.
I don't advise playing with this game if you aren't prepared for something to happen, or if you're so prepared that you've got satanic symbols scrawled on your wall with the black mass being perpetually looped on your computer...y'know...just in case something does happen. Winky face, grin. I do not use emoticons, so you'll just have to accept the verbal description of my facial expressions.