Pre-cana is basically a marriage preparation course offered to couples planning for marriage in the catholic church. If you have found a compatible partner and you are now planning to get married to the love of your life you will be required to take a marriage course to expose you to some of the critical discussions into the marriage life.
You need to be trained on how to live happily with your wife. In case you engage in some quarrels, you are trained on how you would handle such conversations and ensure that you are at peace with each other. The pre-can course is meant to train you on every aspect of the marriage life based on the catholic teachings.