Bacchanalia is like a big party, where people celebrate and have fun by drinking lots of wine and eating delicious food. It happens during a special time of the year in ancient Rome, and it is like a time when everyone can let loose and have fun. People wear special clothes, and there is music and dancing. Imagine it like your birthday party, but for a whole bunch of people, and they all get to have a lot of fun together! But nowadays, we don't have Bacchanalias anymore - they are just something people used to do a long time ago.