I think a little better description of it is that it's swimming, and sailing, and fishing, and horseback riding, and all sorts of other fun things for kids to do. So a lot of the kids go back for years until they are in high school, at which point, some transition to being counselors at the camp. But these camps are very expensive. So, as @C-Man mentioned, later, when some of these kids end up at large Texas universities like UT, some of them know each other and end up in fraternities or sororities together or get recommended for bids to these organizations because they knew each other from years of going to summer camp together.
I wouldn't call it weird for what it is at its base. It's just fun shit for kids to do during the summer. But because it's expensive and there are limited spots available (and because people have been attending for generations, it is exclusive and because of that, it feeds into the exclusivity of fraternities and sororities later.