A Fundraiser item is where students can collectively contribute their coins towards a cause to meet a goal.  A good example of this would be making a donation to a charity (Red Cross below).  The green progress bar communicates the percentage reached towards the goal.

There doesn't have to be a monetary value attached to the Fundraiser.  You can use it to reach other goals, such as "Raise 2000 coins and we'll order in lunch".  The currency symbol and value are optional (below):

If the Goal is met, a banner will be placed on the listing in the store.  It is up to you how to communicate to your users about the next steps you'll take to honor this fundraiser.