A parade is a group of people marching in ceremony, celebration, or protest. Often a parade involves fire trucks, costumed adults throwing candy to children, baton twirlers, and members of the armed forces.
Parade is also a verb, meaning to walk or march ostentatiously. When your sister first brings home her prom dress, she might parade around the living room after putting it on so everyone can see it. As a noun parade is an event in which a whole lot of people march in the streets — they could be wearing prom dresses, but more likely they're celebrating of a holiday or taking part in a military action.