There are three types:
Brewery Pages: All check-ins to all beers by the brewery irrespective of where the user has tagged the location (Example: https://untappd.com/greatlakesbreweryca). You can manage this page if you work for the brewery (How To: Claim Brewery). Duplicate brewery pages can be merged.
Beer Pages: All check-ins to a selected beer, irrespective of where the user has tagged their location (Example https://untappd.com/b/great-lakes-brewery-pompous-ass-epa/7028). You can not manage a beer page, but you can edit/manage the beer if you have claimed the brewery it belongs to.
Venue Pages: All check-ins to that venue, irrespective of what beer the user had. (Example: https://untappd.com/venue/518). You can mange this venue page if you have an Untappd for Business subscription, you can find out more about that by submitting your contact information here: untappd.com/business