Bar rule is played mostly in bars. No kidding!
In bar rule, you can hit your opponent' ball even without hitting any balls are still ok. If you make a foul, there is no any "ball in hand", just place the cue ball anywhere behind the foot line and the cue ball must be shot forward. You have to call the ball and pocket before shooting which is same as the valley rule ............... but, you are also required to call the ball you want to shoot is "straight in" to the pocket or not.
Not everybody like Bar Rule, same as not everyone like valley rule.
I don't think you'll find many people here who like bar rules over bca/vnea/wpa rules around here. There's a reason why every sanctioned leaague and tournament plays by some form of BCA rules.
There is no such thing as a standard bar rules. I have found that the losing player will always be the ref. and inform the winning player that they made a foul or did or doing something not allowed.