"Pioneers" are the socialist world's equivalent of Boy Scouts. Except in addition to practical stuff you would learn, you'd also get a strong dose of overt political indoctrination.

For example, all pioneers recite the motto "Pioneers for Communism, we shall be like Che!" (Pioneros por el Comunismo, Seremos como el Che).

The basic idea behind the organization is to have a youth oriented organization that serves the very, very young. It molds kids to be ideal (socialist) citizens. In theory, kids will start as Pioneers, go on to the Communist Youth, and finally join the actual Communist Party as mature adults. Each organization has its own characteristics, purpose, and rules, and normalizes/inculcates government sponsored views on politics, economics, and society in general.

There were also international exchanges which involved pioneers from one country going to pioneer congresses in other Socialist countries with their peers from those countries. It served to reinforce a sense of belonging to a broader socialist movement/world. There is even a special gesture, akin to a military salute, that kids do, which can be seen here (the girl in the middle is doing the gesture best).

You can see glimpses of the broader Pioneer movement in Nikita Mikhalov's 1994 film Anna, which is a documentary about his daughter growing up and his thoughts (as a Soviet filmmaker) on the fall of the USSR. Part of the film shows one idealized pioneer congress and how kids from different socialist countries interacted, what the uniform looks like, etc.

Edit: As I never participated in a Pioneer camp myself I can't tell you much about their set-up, unfortunately. There would also be a huge gap between the Cold War era Pionero organization, which had international travel and resources for camp within Cuba, and post-1991 Pioneros, which is running on a shoe-string budget and seems to have been largely collapsed into elementary school generally. There are still Cuban Pioneer congresses at the municipal, provincial, and national level, but how much this involves camping and where said camps would be is beyond me. Sorry.