Beach is a nicer way of expressing your anger. It can be said in place of any "bad" word that you can think of. Whenever your thinking a "bad" thought, it is always nice to resort to beach. Mostly because there might be children around. Also, it doesn't give you the risk of saying something you would regret. A little too often, we take out our anger on beloved family members. By using beach, you are staying away from those "bad" words and taking out your anger in a good way.
The concept of boudoin is to greet someone. You use boudoin in the same context as you would to simply say hi or bye to someone. In other words, boudoin is put in place of hi or bye in each and every conversation.