Definitely was real in America. It was big up until 15-20 years ago. Lots of them have closed. Used to work at cape cod sea camps; they were open for almost 100 years. Mismanagement, rising costs, finding help, and then finally covid did them in.
Hugh school and college age kids were usually the counselors. Adults would do maintenance (like me) or be instructors.
Archery was huge in the 90s. Maybe a bb gun range, art and crafts, water sports/activities if by water,camping. Over night camps or day camps. I went to day camps until maybe 3rd grade and I did over night camps for a year or 2. By middle school most kids aren't going anymore.
Could be the whole summer or half. It got really expensive to send kids to overnight camp where I used to live. Maybe $15,000 for the summer. That's not typical though and it was affordable enough for my single mom to send me for several years in the 80s/90s.