Rather than offering a unit of usage time at a particular resort or property, Holiday Clubs and Vacation Clubs are programs that offer timeshare weeks at a number of (oftentimes international) resorts within a particular network.
Many vacation clubs utilize a points program, which, rather than assigning owners a specific week and resort that they may use each year, assigns owners a certain number of points. These points can then be used to "purchase" time at one of the in-network properties each year. Owners can choose to visit a different in-network resort each time their points renew, or they can "bank" or save up points to vacation at more luxurious or highly-desirable resorts, or during more desirable travel seasons. Not all vacation clubs work off a points program; some allow for straight week-to-week exchange, so it's important to consult with your resort or timeshare reseller to determine which method your club uses.
Popular examples of Holiday or Vacation Clubs include Marriott, Hilton Grand Vacations Club, Worldmark by Wyndham and Hyatt. Ownership with a property within one of these clubs generally grants access to many of their other resorts, but it is important to be clear on your arrangement. For example, Marriott does not allow owners to participate in their points program, which allows for free movement within the network, if they've purchased their property resale. In this case, owners would need to secure a membership with a third-party exchange company to trade. It's important to discern individual resort policies, especially those regarding resale, before you buy timeshare with a Holiday Club or Vacation Club.