In climbing competitions there are usually the familiar competitor categories of beginner, intermediate, and advanced. Sometimes there are categories for youth or older climbers too. At bigger competitions there will be an "open" category which has routes harder than some found in the advanced category.
Does anyone know why that category was originally called "open"?
Disclaimer: My Answer is based off Canada's Tour de Bloc structure.
My understanding for the use of the term Open is that it is "Open" to anyone who wants to give it a go. If you are not vying for a spot on the Canadian team you would go Recreational or Experienced.
The Open category is for the top climbers who are serious about competing.
Open competitors vie for points based on their ranking at each comp, and the total points over the entire season determines the selection of Canada’s national climbing team. At each comp the open competitors first do a Qualifying round; the top 6-8 men and women then advance to a final round where they face 4 or 5 new problems that they have not seen before (called “isolation format”). The finals are always an exciting spectacle for all the other climbers to watch.
In general sport terms "Open" is the primary competitive group. Anyone can enter.
There may be other groups that anyone can enter, like "Recreational" or restricted entrance groups like "Under 21s", "Men"*, "Ladies", "Masters" (usually over age 35 depending on sport), but if there's an open category and you're competitive, that's the one to be in.
*Usually if there's an "Open", there won't be a "Men"
I used to run climbing comps approximately 15 years ago and the categories were always U12, U14, U16, U18, Open, and Masters. In elite competitions as mentioned in another answer Open was open to anyone who wanted to prove they were the best. In our comps, occasionally these were competitors who could have climbed in age groups, but wanted to climb in the open category instead (or as well, depending on the competition).
I think more recently there is a drive to make competitions more fun and social (and get more entrants and more money) hence the introductions of the social categories you have mentioned, but these sit independently of the elite level age based system.
Open is a common term in sports tournaments.
It is a class that is open to anyone that wants to sign up.
Typically even pros can enter an open division but some tournaments may exclude pros from Open.
For a club type event it also means you don't have to be member of the club (or country). British Open, US Open, ....
