Larger sagre (the plural of sagra) may feature musical bands and perhaps a competition of some sort, like a bike race.
Attending a sagra is a way to get a taste of Italian country life. You order food to be cooked by locals with a passion for the local cuisine, then sit at communal tables to eat.
You'll probably need a car to attend a sagra, as most of them are held in small towns, usually in the main piazza. When you drive through the Italian countryside, you'll see colorful posters posted at intersections indicating the sagra di ____, with the dates and times large enough to be read from a passing car. They're in Italian, of course, but they're pretty easy to figure out. See Reading a Sagra Poster to see the kinds of information you can glean from one.