What is the difference between a ''bridal shower'' and a ''bachelorette party''?

No problem asking.

A Bridal Shower is traditionally a party where female guests are invited and bring gifts for the Bride. Sometimes, showers are co-ed and allow men to attend too, but usually it is just women. You would invite ladies of all ages, Moms, Aunts, Grandmas as well as friends. The people invited are also to be invited to the wedding.

The Bachelorette Party is usually a much smaller group of people, usually your Bridemaids and MOH, plus a few others if you'd like. It is more "for fun". No gifts. It can be a night out for a nice dinner; club hoping; a spa day; etc.

What Kathy said. Also, showers are typically held in the afternoon opposed to the bachelorette party is usually in the evening/night unless you choose to do a spa day type thing as Kathy suggested.